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Synthesis, Characterization and Utilization of New Diorganohydrazido(2-) Tungsten Complexes as Single-Source Precursors ...

Permanent Link: http://ufdc.ufl.edu/UFE0022814/00001

Material Information

Title: Synthesis, Characterization and Utilization of New Diorganohydrazido(2-) Tungsten Complexes as Single-Source Precursors for MOCVD of WNxCy Thin Films
Physical Description: 1 online resource (165 p.)
Language: english
Creator: Koller, Juergen
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: amidinate, barrier, copper, cvd, diffusion, film, guanidinate, hydrazido, mocvd, nitride, thin, tungsten
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: New diorganohydrazido(2-) tungsten complexes have been synthesized by reaction of the corresponding 1,1-diorganohydrazine with WCl6 and subsequent treatment with a coordinating solvent to yield the target compounds (L)Cl4W?NNR2 (R2 = Me2, -(CH2)5-, Ph2; L = py, MeCN). The compounds were characterized by 1H and 13C NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction, then subsequently used as single-source precursors for the MOCVD of WNxCy thin films. NMR kinetic studies in combination with mass spectrometry and thermogravimetric analysis (TGA) confirmed acetonitrile dissociation to be a facile decomposition pathway under CVD conditions (T > 300 ?C). Film depositions were carried out in a custom-built cold wall CVD reactor by injection of the precursor dissolved in benzonitrile. All experiments were carried out in a temperature range from 300 to 700 ?C. The deposited films, consisting of tungsten, nitrogen, carbon and oxygen, were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and 4-point probe. Film compositions revealed that N-incorporation was improved compared to films deposited from the related tungsten imido precursors (CH3CN)Cl4W?NR (R = iPr, Ph, allyl). Viability of the deposited films as Cu diffusion barriers was evaluated by depositing 100 nm of PVD Cu onto the diffusion barrier followed by annealing of the PVD Cu/WNxCy /Si (100) tri-stack at elevated temperatures (500 ?C). The effect of ammonia (NH3) on film properties was studied by addition of NH3 into the carrier gas during CVD experiments. Film properties were determined by XPS, XRD, SEM and 4-point probe. Compositional data revealed an increase in N-incorporation into the produced films when NH3 was used as a co-reactant. Additionally, lower growth rates and less carbon/oxygen incorporation were observed. Annealing and XPS depth profiling were used to assess the quality of the produced films as Cu diffusion barriers. Mixed hydrazido guanidinate tungsten complexes were prepared and characterized by 1H and 13C NMR, mass spectrometry and single-crystal X-ray diffraction. X-ray studies were used to quantify the bonding behavior of the guanidinate ligands in the synthesized compounds. Mass spectrometry gave some insight into possible fragmentation pathways of these complexes.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Juergen Koller.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: McElwee-White, Lisa A.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022814:00001

Permanent Link: http://ufdc.ufl.edu/UFE0022814/00001

Material Information

Title: Synthesis, Characterization and Utilization of New Diorganohydrazido(2-) Tungsten Complexes as Single-Source Precursors for MOCVD of WNxCy Thin Films
Physical Description: 1 online resource (165 p.)
Language: english
Creator: Koller, Juergen
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2008

Subjects

Subjects / Keywords: amidinate, barrier, copper, cvd, diffusion, film, guanidinate, hydrazido, mocvd, nitride, thin, tungsten
Chemistry -- Dissertations, Academic -- UF
Genre: Chemistry thesis, Ph.D.
bibliography   ( marcgt )
theses   ( marcgt )
government publication (state, provincial, terriorial, dependent)   ( marcgt )
born-digital   ( sobekcm )
Electronic Thesis or Dissertation

Notes

Abstract: New diorganohydrazido(2-) tungsten complexes have been synthesized by reaction of the corresponding 1,1-diorganohydrazine with WCl6 and subsequent treatment with a coordinating solvent to yield the target compounds (L)Cl4W?NNR2 (R2 = Me2, -(CH2)5-, Ph2; L = py, MeCN). The compounds were characterized by 1H and 13C NMR spectroscopy, mass spectrometry and single crystal X-ray diffraction, then subsequently used as single-source precursors for the MOCVD of WNxCy thin films. NMR kinetic studies in combination with mass spectrometry and thermogravimetric analysis (TGA) confirmed acetonitrile dissociation to be a facile decomposition pathway under CVD conditions (T > 300 ?C). Film depositions were carried out in a custom-built cold wall CVD reactor by injection of the precursor dissolved in benzonitrile. All experiments were carried out in a temperature range from 300 to 700 ?C. The deposited films, consisting of tungsten, nitrogen, carbon and oxygen, were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM) and 4-point probe. Film compositions revealed that N-incorporation was improved compared to films deposited from the related tungsten imido precursors (CH3CN)Cl4W?NR (R = iPr, Ph, allyl). Viability of the deposited films as Cu diffusion barriers was evaluated by depositing 100 nm of PVD Cu onto the diffusion barrier followed by annealing of the PVD Cu/WNxCy /Si (100) tri-stack at elevated temperatures (500 ?C). The effect of ammonia (NH3) on film properties was studied by addition of NH3 into the carrier gas during CVD experiments. Film properties were determined by XPS, XRD, SEM and 4-point probe. Compositional data revealed an increase in N-incorporation into the produced films when NH3 was used as a co-reactant. Additionally, lower growth rates and less carbon/oxygen incorporation were observed. Annealing and XPS depth profiling were used to assess the quality of the produced films as Cu diffusion barriers. Mixed hydrazido guanidinate tungsten complexes were prepared and characterized by 1H and 13C NMR, mass spectrometry and single-crystal X-ray diffraction. X-ray studies were used to quantify the bonding behavior of the guanidinate ligands in the synthesized compounds. Mass spectrometry gave some insight into possible fragmentation pathways of these complexes.
General Note: In the series University of Florida Digital Collections.
General Note: Includes vita.
Bibliography: Includes bibliographical references.
Source of Description: Description based on online resource; title from PDF title page.
Source of Description: This bibliographic record is available under the Creative Commons CC0 public domain dedication. The University of Florida Libraries, as creator of this bibliographic record, has waived all rights to it worldwide under copyright law, including all related and neighboring rights, to the extent allowed by law.
Statement of Responsibility: by Juergen Koller.
Thesis: Thesis (Ph.D.)--University of Florida, 2008.
Local: Adviser: McElwee-White, Lisa A.
Electronic Access: RESTRICTED TO UF STUDENTS, STAFF, FACULTY, AND ON-CAMPUS USE UNTIL 2010-12-31

Record Information

Source Institution: UFRGP
Rights Management: Applicable rights reserved.
Classification: lcc - LD1780 2008
System ID: UFE0022814:00001


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SYNTHESIS, CHARACTERIZATION AND UTILIZATION OF NEW DIORGANOHYDRAZIDO(2-) TUNGSTEN COMPLEXES AS SINGLE-SOURCE PRECURSORS FOR MOCVD OF WNXCY THIN FILMS By JRGEN KOLLER A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLOR IDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2008 1

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2008 Jrgen Koller 2

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To my mom and dad 3

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ACKNOWLEDGMENTS First, I would like to thank my advisor Prof. Lisa McElwee-White. During a tough time in my graduate education, she supplied me with in valuable support and honesty which helped me make the right decisions. She has been a true in spiration from Day one as an advisor and never failed to amaze me during scientific discussions Without her guidance and support I would not be in the position I am now, as a scientist. I would also like to thank Dr. Khalil Abboud who always had an open door for me, no matter what the na ture of my problems. Besides the fact that he helped me become knowledgeable of X-ray crystallography, our discus sions helped me grow tremendously as a person. I would also like to thank th e McElwee-White group members who accepted me into their group after my nontraditional entry. They are a pleasure to work with and are always willing to help with problems of any kind. Additionally, I would like to thank Dr. Hiral Ajmera and Dojun Kim from the Department of Chemical Engineeri ng at the University of Florida for all their work. I would like to take this opportuni ty to thank my parents, Aloi s and Resi Koller, for setting a solid foundation for my life. They provided me with love and morals that made me the person I am today. Their unconditional support throughout my years of studies has made it possible for me to go all the way. I would also like to thank my sister, Julia Koller, who is always there for me and can put a smile on my face at any time. Last but not least, I want to thank my fian ce, Cosima Boswell. She provided me with strength behind the scene and backed me up in whatever decisions I made. Her unconditional love and support carried me through all the ups and downs of graduate school and made it possible for me to complete this doctoral program. 4

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TABLE OF CONTENTS page ACKNOWLEDGMENTS ............................................................................................................... 4LIST OF TABLES ...........................................................................................................................8LIST OF FIGURES .........................................................................................................................9ABSTRACT ...................................................................................................................... .............13 CHAPTER 1 INTRODUCTION ................................................................................................................ ..15Thin Films .................................................................................................................... ...........15Overview ...................................................................................................................... ...15Refractory Metal Nitrides ................................................................................................15Chemical Vapor Deposition ...................................................................................................16Evolution of CVD Precursor Design ......................................................................................17Co-reactant Based De sign Strategies ...............................................................................17Single-Source Precursors .................................................................................................18Early design strategies ..............................................................................................18Advanced precursor designs .....................................................................................19Hydrazine derivatives as co-reactants ......................................................................21Thin Film Deposition Mechanisms ........................................................................................22Precursor Delivery ...........................................................................................................22Reactions at the Substrate ................................................................................................23Possible Decomposition Pathways ..................................................................................25, and -Hydrogen abstractions .............................................................................25 -Alkyl elimination ..................................................................................................28Co-reactant induced decomposition .........................................................................29High energy decomposition routes ...........................................................................30Case Study: BTBTT and BTBDT ...........................................................................................30Deposition of WNx Film from BTBTT ...........................................................................31Depositions from BTBDT ...............................................................................................35Conclusions .....................................................................................................................362 SYNTHESIS AND CHARACTERIZAT ION OF DIORGA NOHYDRAZIDO(2-) TUNGSTEN COMPLEXES ..................................................................................................38Diorganohydrazido(2-) Complexes of Early Transition Metals .............................................38Synthesis of Diorganohydrazido (2-) Tungsten Complexes ....................................................38X-Ray Crystallography Study .................................................................................................39Thermogravimetric Analysis ..................................................................................................48Nuclear Magnetic Resonance Spectroscopy Investigation .....................................................48Mass Spectrometry .................................................................................................................49 5

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Experimental Procedures and Syntheses ................................................................................51General Procedures ..........................................................................................................51Synthesis of (CH3CN)Cl4W NNMe2 ( 24) ......................................................................51Synthesis of (CH3CN)Cl4W N-pip ( 25) .........................................................................52Synthesis of (CH3CN)Cl4W NNPh2 ( 26) .......................................................................52Synthesis of (py)Cl4W NNPh2 ( 27) ................................................................................53NMR Spectroscopy .........................................................................................................53Thermogravimetric Analysis ...........................................................................................54Mass Spectrometry ..........................................................................................................54Crystallographic Studies ..................................................................................................54X-ray data collection and structure refinement for 24 .............................................54X-ray data collection and structure refinement for 25 .............................................55X-ray data collection and structure refinement for 26 .............................................55X-ray data collection and structure refinement for 27 .............................................563 METAL-ORGANIC CHEMICAL VAPOR DEPOSITION OF WNxCy THIN FILMS ........58Film Growth and CVD Reactor Design ..................................................................................58Characterization Techniques ..................................................................................................59Film Depositions from 24 25, and 26 ....................................................................................59Film Composition ............................................................................................................60X-Ray Diffraction ............................................................................................................6 4Growth Rates ...................................................................................................................66Diffusion Barrier Testing ................................................................................................70Conclusions .............................................................................................................................74Experimental Procedures ....................................................................................................... .75Film Deposition ............................................................................................................... 75Film Characterization ......................................................................................................75Diffusion Barrier Testing ................................................................................................764 EFFECT OF NH3 ON FILM PROPERTIES OF MOCVD WNxCy DEPOSITED FROM 25 AND 26 ..............................................................................................................................78Introduction .................................................................................................................. ...........78Film Deposition from 25 and 26 with NH3 ............................................................................78X-Ray Diffraction ............................................................................................................7 9Film Composition ............................................................................................................81Chemical Bonding States ................................................................................................84Growth Rates ...................................................................................................................89Film Resistivity .............................................................................................................. .91Atomic Force Microscopy ...............................................................................................92Diffusion Barrier Testing ................................................................................................93Conclusions .............................................................................................................................96Experimental Procedures ....................................................................................................... .97Film Deposition ............................................................................................................... 97Film Characterization ......................................................................................................97Diffusion Barrier Testing ................................................................................................98 6

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5 SYNTHESIS AND CHARACTERIZAT ION OF DIORGA NOHYDRAZIDO(2-) GUANIDINATE/AMIDINATE TUNGSTEN COMPLEXES ............................................100Guanidinate/Amidinate Complexes in MOCVD ..................................................................100Synthesis of Diorganohydrazido(2-) Guan idinate/Amidinate Tungsten Complexes ...........101X-Ray Crystallography Study ...............................................................................................103Mass Spectrometry ...............................................................................................................106Alternate Synthetic Pathways ...............................................................................................107Modified Lithium Guanidinate Reagents ......................................................................107Synthesis .................................................................................................................108X-ray crystallography study ...................................................................................108Amidines ...................................................................................................................... ..109Experimental Procedures and Syntheses ..............................................................................112General Procedures ........................................................................................................112Synthesis of [iPrNC(NMe2)NiPr]Cl3W NNMe2 ( 28) ...................................................113Synthesis of [iPrNC(Me)NiPr]Cl3W NNMe2 ( 29)........................................................113Synthesis of [iPrNC(Me)NiPr]Cl3W N-pip ( 30) ...........................................................114Synthesis of [iPrNC(Me)NiPr]Cl3W NNPh2 ( 31) .........................................................115Synthesis of [TMEDA]Li{iPrNC[N(SiMe3)2]NiPr} ( 32) ..............................................115Synthesis of H[iPrNC(Me)NiPr] ( 33) ............................................................................116Mass Spectrometry ........................................................................................................116Crystallographic Studies ................................................................................................117X-ray data collection and structure refinement for 28 ...........................................117X-ray data collection and structure refinement for 32 ...........................................117 APPENDIX A TABLES OF CRYSTALLOGRAPHIC DATA ...................................................................119Crystallographic Data for (CH3CN)Cl4W NNMe2 ( 24) ......................................................119Crystallographic Data for (CH3CN)Cl4W N-pip ( 25) .........................................................123Crystallographic Data for (CH3CN)Cl4W NNPh2 ( 26) .......................................................128Crystallographic Data for (py)Cl4W NNPh2 ( 27) ................................................................137Crystallographic Data for [iPrNC(NMe2)NiPr]Cl3W NNMe2 ( 28) .....................................142Crystallographic Data for [TMEDA]Li{iPrNC[N(SiMe3)2]NiPr} ( 32) ................................146B NMR KINETICS DATA FOR COMPOUND 24 ................................................................154LIST OF REFERENCES .............................................................................................................155BIOGRAPHICAL SKETCH .......................................................................................................165 7

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LIST OF TABLES Table page 2-1. Selected bond distances () and angles () for 24. ...............................................................412-2. Selected bond distances () and angles () for 25. ...............................................................412-3. Selected bond distances () and angles () for 26. ...............................................................412-4. Selected bond distances () and angles () for 27. ...............................................................422-5. Crystal data and struct ure refinement for compounds 24 27. .............................................462-6. Summary of relative abundances for positive ion CI mass spectra of compounds 24 26........................................................................................................................................504-1. Literature values of relevant binding energies. .....................................................................865-1. Selected bond distances () and angles () for 28. .............................................................1045-2. Crystal data and refinement for compound 28 ...................................................................1055-3. Summary of relative abundances for positive ion CI mass spectra of compounds 29 31......................................................................................................................................1075-4. Selected bond distances () and angles () for 32. .............................................................1095-5. Crystal data and refinement for compound 32 ...................................................................110 8

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LIST OF FIGURES Figure page 1-1. Single-source precursor s for the deposition of metal nitride films. ......................................181-2. Advanced precursor designs. .................................................................................................201-3. Precursors for the deposition of WNxCy films. ......................................................................201-4. Examples of transiti on metal hydrazido complexes. .............................................................221-5. Schematic diagram of mech anisms during a CVD reaction. .................................................241-6. Mechanism of -hydrogen abstraction. .................................................................................261-7. Mechanisms for -hydrogen elimination and -hydrogen abstraction. .................................271-8. Mechanism for -hydrogen abstraction. ................................................................................281-9. Mechanism for -alkyl elimination. ......................................................................................291-10. Formation of tBuNH2 from BTBTT via -H abstraction. ...................................................311-11. Reaction kinetics of BTBTT decomposition. ......................................................................321-12. Formation of isobutylene from 15 via -H abstraction. .......................................................331-13. Formation of acetontrile from 15 via successive -methyl abstractions. ............................331-14. Structure of 20 with a W4N4 skeleton. .................................................................................351-15. Formation of EtN=CHCH3 from BTBDT via -H elimination. ..........................................362-1. Synthesis of compounds 24 27. ..........................................................................................392-2. Possible resonance structures of diorganohydrazido(2-) complexes. ....................................402-3. Thermal ellipsoids diagram of the molecular structure of 24. ...............................................422-4. Thermal ellipsoids diagram of the molecular structure of 25. ...............................................432-5. Thermal ellipsoids diagram of the molecular structure of 26. ...............................................442-6. Thermal ellipsoids diagram of the molecular structure of 27. ...............................................452-7. TGA curve of compounds 24 26 recorded at a heating rate of 10 C/min under nitrogen. ..................................................................................................................... ........48 9

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2-8. Plot of ln(k/T) vs. 1/T for acetonitrile exchange in complex 24. ..........................................493-1. Schematic diagram of the CVD reactor. ................................................................................583-2. Composition of films deposited from 24 on Si (100) substrate at different deposition temperatures determined by AES after 0.5 min of sputtering. ..........................................613-3. Composition of films deposited from 25 on Si (100) substrate at different deposition temperatures determined by XPS after 10 min of sputtering. ............................................623-4. Composition of films deposited from 26 on Si (100) substrate at different deposition temperatures determined by XPS after 10 min of sputtering. ............................................633-5. X-ray diffraction patterns for films deposited from 24 between 300 and 700 C on Si (100) substrate. ...................................................................................................................653-6. X-ray diffraction patterns for films deposited from 25 between 250 and 700 C on Si (100) substrate. ...................................................................................................................653-7. X-ray diffraction patterns for films deposited from 26 between 300 and 700 C on Si (100) substrate. ...................................................................................................................663-8. SEM images for films deposited from 24 at 400 and 650 C on Si (100) substrate. ............673-9. Arrhenius plot for film depositions from 24 on Si (100) substrate. ......................................683-10. SEM images for films deposited from 25 at 300 and 700 C on Si (100) substrate. ..........683-11. Arrhenius plot for film depositions from 25 on Si (100) substrate. ....................................693-12. SEM images for films deposited from 26 at 400 and 600 C on Si (100) substrate. ..........693-13. Arrhenius plot for film depositions from 26 on Si (100) substrate. ....................................703-14. Preand post-anneal AES depth profile of Cu/WNxCy /Si (100) stack for WNxCy film deposited from 24. .............................................................................................................713-15. Preand post-anneal XRD measurement of Cu (100 nm)/WNxCy/Si stack for WNxCy film deposited from 25 at 400 C. ......................................................................................723-16. Post-anneal AES depth profile of the Cu/WNxCy/Si stack for WNxCy film deposited from 25. ............................................................................................................................. .733-17. Evaluation of barrier perfor mance of films deposited from 26. ..........................................744-1. X-ray diffraction patterns for films deposited from 25 and NH3 between 300 and 700 C on Si (100) substrate. ....................................................................................................79 10

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4-2. X-ray diffraction patterns for films deposited from 26 and NH3 between 300 and 700 C on Si (100) substrate. ....................................................................................................804-3. Comparison of film composition deposited from 25 with NH3 (blue) and without NH3 (red) on Si (100) substrate at different deposition temperatures determined by XPS after 10 min of sputtering. ..................................................................................................824-4. Dependence of N/W ratios on depositi on temperature for films deposited from 25 with and without NH3. ...............................................................................................................834-5. Comparison of film composition deposited from 26 with NH3 (blue) and without NH3 (red) on Si (100) substrate at different deposition temperatures determined by XPS after 10 min of sputtering. ..................................................................................................844-6. Evolution of binding energies (W 4f) w ith deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. ...............854-7. Evolution of binding energies (N 1s) w ith deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. ...............874-8. Evolution of binding energies (C 1s) w ith deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. ...............884-9. Evolution of binding energies (O 1s) w ith deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. ...............884-10. SEM images for films deposited from 25 and NH3 at 300 and 600 C on Si (100) substrate. ............................................................................................................................894-11. Arrhenius plot for film depositions from 25 and NH3 on Si (100) substrate. ......................904-12. SEM images for films deposited from 26 and NH3 at 400 and 600 C on Si (100) substrate. ............................................................................................................................904-13. Arrhenius plot for film depositions from 26 and NH3 on Si (100) substrate. ......................914-14. Change of resistivity with depos ition temperature for films deposited from 25 with and without NH3. ...............................................................................................................924-15. AFM images of films deposited from 26.............................................................................934-16. Preand post-anneal XRD measurement of Cu (100 nm)/WNxCy/Si stack for WNxCy film deposited from 25 at 400 C. ......................................................................................944-17. Post-anneal AES depth profile of the Cu/WNxCy/Si stack for WNxCy film deposited from 25 and NH3. ...............................................................................................................944-18. TEM images of the Cu/WNxCy/Si stack. .............................................................................95 11

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4-19. EDS profile of the Cu/WNxCy/Si stack after annealing under N2 at 500 C for 30 min. ....965-1. Generic ligand structures. .............................................................................................. ......1005-2. Possible decomposition pathways of me tal guanidinate complexes during CVD. .............1015-3. Synthesis of compounds 28 31. ........................................................................................1025-4. Thermal ellipsoids diagram of the molecular structure of 28. .............................................1045-5. Synthesis of compound 32. ..................................................................................................1085-6. Thermal ellipsoids diagram of the molecular structure of 32. .............................................1115-7. Synthesis of compound 33. ..................................................................................................112 12

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Abstract of Dissertation Pres ented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy SYNTHESIS, CHARACTERIZATION AND UTILIZATION OF NEW DIORGANOHYDRAZIDO(2-) TUNGSTEN COMPLEXES AS SINGLE-SOURCE PRECURSORS FOR MOCVD OF WNXCY THIN FILMS By Jrgen Koller December 2008 Chair: Lisa McElwee-White Major: Chemistry New diorganohydrazido(2-) tungsten complexes have been synthesized by reaction of the corresponding 1,1-diorganohydrazine with WCl6 and subsequent treatment with a coordinating solvent to yield the target compounds (L)Cl4W NNR2 (R2 = Me2, -(CH2)5-, Ph2; L = py, MeCN). The compounds were characterized by 1H and 13C NMR spectroscopy, mass spectrometry and single crystal X-ray diffr action, then subsequently used as single-source precursors for the MOCVD of WNxCy thin films. NMR kinetic studies in combination with mass spectrometry and thermogravimetric analysis (TGA) confirmed acetonitrile dissociation to be a facile decomposition pathway under CVD conditions (T >300 C). Film depositions were carried out in a custom -built cold wall CVD reactor by injection of the precursor dissolved in benzonitrile. All expe riments were carried out in a temperature range from 300 to 700 C. The deposited films, c onsisting of tungsten, ni trogen, carbon and oxygen, were characterized by X-ray photoelectron spectroscopy (XPS) X-ray diffraction (XRD), scanning electron microscopy (SEM) and 4-point probe. Film compositions revealed that Nincorporation was improved co mpared to films deposited fr om the related tungsten imido precursors (CH3CN)Cl4W NR (R = iPr, Ph, allyl). Viability of the deposited films as Cu 13

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14 diffusion barriers was evaluated by depositing 10 0 nm of PVD Cu onto the diffusion barrier followed by annealing of the PVD Cu/WNxCy /Si (100) tri-stack at elevated temperatures (500 C). The effect of ammonia (NH3) on film properties was studied by addition of NH3 into the carrier gas during CVD experiments. Film prope rties were determined by XPS, XRD, SEM and 4-point probe. Compositional data revealed an increase in N-incorporation into the produced films when NH3 was used as a co-reactant. Additio nally, lower growth rates and less carbon/oxygen incorporation were observed. Ann ealing and XPS depth profiling were used to assess the quality of the produced films as Cu diffusion barriers. Mixed hydrazido guanidinate tungsten complexe s were prepared and characterized by 1H and 13C NMR, mass spectrometry and single-crystal Xray diffraction. X-ray studies were used to quantify the bonding behavior of the guanidina te ligands in the synthesized compounds. Mass spectrometry gave some insight into possible fragmentation pathways of these complexes.

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CHAPTER 1 INTRODUCTION Thin Films Overview Over the last few decades, countless electroni c devices (personal computers, cell phones, etc.) have made their way into the everyday lives of people. The steady demand for smaller but yet more powerful versions of these gadgets fo rces the semiconductor industry to continuously downscale the size of integrated circuits (ICs), which comprise the he arts of many of these devices. Thin films have become increasingly important in this miniaturization process as they represent the micro/nano-si zed building blocks used to constr uct countless ICs. This trend has sparked increased interest in the fundamental science and unde rstanding of new materials for thin film applications as well as their development. Furthermore, widespread use of thin films in numerous other applications su ch as photovoltaic cells, flat panel displays, storage devices, coatings, etc. makes this fast growing area of science appealing for both academia and industry.1 In addition to the discovery of novel mate rials themselves, the corresponding deposition techniques are equally important since they represent the link between theory and practical application. Therefore, current augmented attention towards deposition techniques and their improvement is not surprising. Refractory Metal Nitrides As miniaturization hit a critical level with the introducti on of 130 nm technology in the late 1990s, industrial manufacturers were forced to st art replacing the aluminum (Al) metallization scheme found in early microelectronics with a copper (Cu) based scheme.1 The lower bulk resistivity of Cu (1.678 -cm) compared to Al (2.655 -cm) combined with greater resistance towards electromigration allows for significantly improved device performance characteristics.2 15

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The high mobility of Cu in silicon (Si) (DCu ~2 x 10-5 cm2/s at 500 C), however, can result in unwanted redistribution of Cu, ultimately degr ading device performance or even causing complete failure.3,4 Thin layers of inorganic materi als acting as diffusion barriers were ultimately chosen to resolve this problem.5,6 Given that titanium n itride (TiN) represented the industrial standard for diffusion ba rrier applications in Al metal lization schemes as well as the available knowledge base due to its extensive us e, refractory metal nitrides such as tantalum nitride (TaNx), tungsten nitride (WNx), and tungsten carbonitride (WNxCy) seemed to be promising candidates for replacing TiN in Cu metallization applications.7 A Ta/TaN bilayer deposited via physical vapor deposition (PVD) t echniques can be found as the diffusion barrier in many of todays microelectronics.8 However, the limitations of PVD force the semiconductor industry to identify alternatives for TaN as manuf acturing is rapidly appro aching transistor sizes of 45 nm.9 Requirements for future diffusion barriers include structural and thermal stability, low diffusivity, acceptable adhesion to Cu and diel ectrics, low resistivity, and resistance towards thermal and mechanical stresses. Thin layers of both WNx 1,10-15 and WNxCy 16-18 are promising barrier candidates based on the aforementioned criteria and have therefore received a considerable amount of attention.19 Chemical Vapor Deposition In recent years, Chemical Vapor Depositi on (CVD) and Metal-Orga nic Chemical Vapor Deposition (MOCVD) have emerged as the i ndustrial standard for many thin film applications.20,21 CVD proceeds through transportation of volatile precursors to a reaction chamber via a carrier gas followed by deposition of a thin layer of inorganic material as a result of thermally induced decomposition reactions of these precursors in the gas phase as well as on the substrate surface. The ability to deposit hi gh purity films at relati vely low temperatures combined with excellent conformality at very high aspect ratios renders CVD the deposition 16

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technique of choice for many mate rials applications. Other advantages of CVD include the availability of a variety of pr ecursors from the entire periodic ta ble as well as reasonably high growth rates for many materials.22-25 A number of variations from standard C VD reactions have emerged over the years allowing for adaptation to the specific needs of each thin film depositi on, with Plasma-Enhanced CVD (PECVD),26-28 Low Pressure CVD (LPCVD), and At mospheric Pressure CVD (APCVD) symbolizing just a few examples. AerosolAssisted CVD (AACVD) in particular has transformed the CVD landscape by opening countless new precursor design strategies since the technique bears less rigorous rest rictions concerning volatility a nd stability of the precursors.29,30 Evolution of CVD Precursor Design Co-reactant Based Design Strategies Much early effort was targeted towards co-reactant based deposition reactions which typically involved the use of two separate reag ents such as metal halid es/carbonyls as the metal source and nitrogen (N2 or NH3) or oxygen (O2) containing gases for metal nitride and metal oxide depositions, respectively. The choice of the metal source was typically governed by the physical properties of the precu rsor; however, commercial availabi lity, eliminating the need for an extensive synthetic effort, was another signifi cant factor. A selection of typical co-reactant based CVD systems used to deposit metal nitride films is shown below. WF6 + NH3 11,31-34 WCl6 + NH3 35,36 W(CO)6 + NH3 36-39 TaCl5 + N2 + H2 + Ar40,41 Although most of these approaches result in the successful deposition of the desired thin films, the formation of reactive byproducts such as HF or HCl, which possess the capability of 17

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etching the substrate and contaminating the de posited films, limit the usefulness of these systems. In addition, handling difficulties due to the high reactivity of metal fluorides and deposition temperatures of >500 C do not meet the requirements of industrial manufacturers. Single-Source Precursors In order to resolve this dilemma, the attention of researchers shifted towards utilization of single-source precursors. These organometall ic compounds contain all the desired elements within one typically monomeric complex and ther efore eliminate the need for a co-reactant. Additionally, less thermal energy is required to decompose organometallic complexes compared to nucleophile/electrophile based depositions, effectively lowering deposition temperatures. Early design strategies Early precursor design focused mainly on stabilit y and volatility which have to be adequate in order to ensure successful transport to the substrate surface. Homoleptically ligated metal complexes can be found in numerous early studies since they typically require the least amount of synthetic effort. Compounds 1 3 (Figure 1-1) represent a se lection of precursors with homoleptic ligand design for the deposition of metal nitride films.42-44 Figure 1-1. Single-source pr ecursors for the deposition of metal nitride films. 18

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Some of the first precursors studied in detail are Ti(NMe2)4 (TDMAT) 1 and Ti(N(CH2)4)4 (TPT) 2 in 1990 by Gordon and co-workers, which we re targeted towards the deposition of TiN films.43 Investigations of carbon contamination obse rved in the deposited films and the possible origin thereof provided the first mechanisti c insight into organometallic precursor decomposition. X-ray photoelectro n spectroscopy (XPS) analysis re vealed the presence of Tibound carbon in films deposited from 1 as a result of Ti-C bond formation via -hydride elimination. On the contrary, only organic carb on was found in films deposited from precursors such as 2 which show geometric restrictions regarding -hydride elimination. Although the understanding of these decomposition pathways wa s far from complete, subsequent precursor designs could be adapted accordingly. Since most CVD experiments relied on vol atilization of the precursor via bubbler techniques, liquid compounds with high vapor pressu res were desirable. Certain trends that encourage the formation of liquid compounds were identified and employed in precursor design. A heterolytic ligand set was know n to discourage crystal packing, thus, complexes were more likely to be in the liquid state.30,45,46 Compound 4, tert -butyl-tris(dimethylamido)titanium (tBuTDMAT) (Figure 1-1), shows the incorporation of a tert -butyl ligand into the coordination sphere of titanium resulting in a modified version of TDMAT w ith improved volatility characteristics.42 Advanced precursor designs As the understanding of precursor decompositi on progresses, advanced design strategies tailored towards specific precursor properties continue to emerge. For deposition of metal nitride films, most precursor designs focus on all-ni trogen coordination spheres to minimize the incorporation of halides in the pr ecursor molecules. As a result, amine-based ligand sets can be found in numerous metal complexes. Since stro ng metal-nitrogen bonds are usually more likely 19

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to survive the deposition proce ss (compared to weaker bonds), it is not surprising that many precursors incorporate ligands which allow formation of metal-nitrogen multiple bonds. Thus, amido (-NR2) ligands, which possess the ability to donate the N lone pair into an empty metal dorbital to strengthen the M-N bond, as well as imido (=NR) ligands with preexisting M-N multiple bonds, can be found in most recent precursors for metal nitride thin film depositions. To illustrate this trend, compounds 5 7 (Figure 1-2) are depicted as representative examples of precursors for the deposition of TiN, TaNx and WNx films, respectively.47-50 Figure 1-2. Advanced precursor designs. Although the incorporation of halides into th e ligand sphere of the metal is typically undesirable, McElwee-White and co-workers ha ve shown that a series of tungsten imido complexes (RCN)Cl4W NR (where R = Me, Ph; R = iPr, allyl, Cy, Ph) ( 8 11) shown in Figure 1-3. Precursors for the deposition of WNxCy films. 20

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Figure 1-3 are not only suitabl e precursors for deposition of WNxCy films but also allow some more insight into precursor decomposition.51-53 Once again, a strong preexisting M-N multiple bond is likely to survive the deposition process to ultimately increase N incorporation into the deposited films. The acetonitrile solvent molecule in the trans position has been shown to be labile presumably due to the strong trans influence of the imido moiety as evidenced by mass spectrometry (MS) and nuclear magnetic resonance (NMR) studies.53-55 In addition, the hydrogen carrier gas reacts with the metalchloride bonds to form HCl gas during film deposition, a postulate that was consistent with both experimental and computational results. Residual gas analysis (RGA) revealed the presence of HCl gas, but not Cl2, as a byproduct of deposition. A relati vely low-energy transition state for bond metathesis was found employing density functi onal theory (DFT) calculations, explaining both the HCl byproduct and the absence of Cl (detec tion limit ~1 at. %) in the produced films as evidenced by XPS.56 Moreover, a correlation between the N-C bond strength of the imido ligand and the fragmentation patterns observed in the MS investigations was established, providing an explanation for the different levels of N inco rporation into the produced films. Finally, a relationship between the N-C bond strength of the corresponding amine and the apparent activation energy (Ea) for film depositions from 8 11 could be established resulting in the identification of the rate determining step (RDS).55 Hydrazine derivatives as co-reactants Despite an early report of the ta ntalum hydrazido complex [Ta(NNMe2)(NHNMe2)(NH2Me2)] by Winter and co-workers in 1994, the us e of hydrazine chemistry in CVD related experiments was slow to develop.57 In recent years, however, thin film depositions using hydrazine derivatives as either co-reactant gases or as mono/di-anionic ligands have reappeared in the literature.58-60 Not only can hydrazines be used as N sources with high N/C ratios, they are 21

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also powerful reducing agents towa rds high valent transition metals.61-64 The rather weak N-N bond (~60 kcal/mol) found in hydrazines promotes d ecomposition via bond cleavage at relatively low temperatures which has allowed researchers to increase the N content of metal nitride films while simultaneously decreasing deposition temperatures.65,66 In addition, incorporation of hydrazine into the coordination sphere of a metal typically increases the vo latility since multiple coordination sites can be occupi ed by few ligand molecules, thus keeping the overall molecular weight of the compound low.67 A variety of different metals have been complexed by various derivatives of hydrazine, however only selected compounds that have found use in MOCVD are shown in Figure 1-4.67,68 Figure 1-4. Examples of transi tion metal hydrazido complexes. Thin Film Deposition Mechanisms Although chemical design strategies of single-source precursors facil itate successful thin film depositions, one has to keep in mind that a CVD process is extraordinarily complex and that every part of the process demands equal cons ideration. The following paragraphs are aimed towards attaining a better understanding of some of the di fferent steps involved in a CVD reaction. Precursor Delivery During a typical CVD process, the precursor is delivered to the reaction chamber along with a carrier gas which can be an inert gas (N2) or a combination of inert and co-reactant gases 22

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(N2/NH3 mixture). A variety of different delivery systems have emerged over the years exploiting the various physical properties of the available precursors Early research efforts were focused on the volatility of the precursor com pounds in question. The transport of these typically liquid compounds to the reactor can be achieved by passing carrier gas through a bubbler assembly containing the precursor. In all cases, sufficiently high vapor pressures are required to sustain reasonable precursor fl ux into the reaction ch amber. Additionally, sublimation can be a useful technique to volatilize solid precursors; however, vapor pressure is once again the determining factor as to whethe r satisfactory growth rates can be achieved. Besides vapor pressure considerations, precursors need to be sufficiently stable to endure the stresses of the transport proce ss to eliminate the possibility of premature decomposition reactions on the sidewalls of the react or and the de livery system. Reactions at the Substrate Although precursor delivery to the reactor can imp ly some engineering related restraints on the potential use of a certain compound, unders tanding the reactions on the substrate surface during deposition prove to be vas tly more challenging from a chem ists point of view. The gasphase reactivity of a complex organometallic compound on or near the gas/ solid interface is yet to be fully understood despite its obvious importance for materials chemistry. Commonly accepted decomposition pathways in organometallic chemistry give some clues as to how precursor disintegration may occur, however, one has to keep in mind that elevated temperatures (>200 C) and the applied partial vacuum during a CVD experiment bear little resemblance to the conditions used for standard mechanistic studies in organometallic chemistry (which are typically performed under roughly ambient conditions). In order to obtain a basic understanding of the chemistry involved in thin film depositio ns, a closer look at the gas/solid interface is 23

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crucial. Figure 1-5 shows a schematic repres entation of the chemistr y taking place at the gas/solid interface. Figure 1-5. Schematic diagram of mechanisms during a CVD reaction.69 Initially, the precursor is transported into th e reaction chamber by means of a carrier gas. Since constant pressure has to be maintained in the reaction vessel, excess gas is removed via a vacuum pump creating a constant flux of gas wh ich in turn generates a main gas flow region encompassing the substrate. In order for a chem ical reaction to occur at the substrate, the precursor molecules have to be transported from the bulk flow area th rough the boundary layer towards the substrate surface. Due to the temperat ure gradient generated by the heated substrate, gas phase reactions of the precursor molecules (unimolecular and/or ca rrier gas-induced) are likely to account for initial precursor decom position, a phenomenon that is also known as gas phase precipitation.70 Following adsorption of intact and/ or partially decomposed precursor 24

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molecules onto the surface, thermally induced complete decomposition of these compounds occurs if the system contains sufficient energy. Gaseous byproducts can desorb from the surface to be removed from the system with the exce ss carrier gas. The chemisorbed species on the surface can form nucleation areas and initiate is land growth which can be considered the early stage of thin film deposition. As deposition c ontinues, the unoccupied areas between these generated growth islands are filled in until a conf ormal layer of material is eventually formed. Possible Decomposition Pathways For chemists, the most intriguing deposition steps in the aforementioned mechanism are the gas phase reactions involving precursor mol ecules and the complete decomposition of the precursor on the substrate surface since existi ng bonds are broken and bonds creating the new material are being formed. Here, the ligand de sign of the precursor molecules has a large influence on the quality of the produced films and the byproducts formed during decomposition. Although caution has to be taken when drawing conclusions, basic organometallic principles can be applied to explain experimental observat ions. Herein, N-bound ligand systems will be discussed preferentially since they are predominantly used for metal nitride film depositions. and -Hydrogen abstractions Although -hydrogen abstraction constitutes an or ganometallic transformation with a generally slower rate compared to other transformations such as -hydrogen elimination, it must be included in this discussion since elevat ed temperatures during CVD experiments demand consideration of higher energy tr ansformations. Furthermore, since Schrock and co-workers reported the occurrence of fast -H elimination in Mo and W alkyl complexes (even though -H atoms are available) this type of transformation cannot be neglected.71 During a typical -H abstraction, a proton is transfe rred from one amido ligand to anot her generating an imido moiety and an amine. This mechanism is generally believed to proceed via a four-membered transition 25

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state which is illustrated in Figure 1-6.72 The newly formed imido ligand is a welcome product of this transformation sin ce the strong metal-nitrogen bond often improves nitrogen incorporation into the resulting films. Figure 1-6. Mechanism of -hydrogen abstraction. Traditionally, -hydrogen elimination has to be cons idered a major mechanistic pathway in transformations of any metal alkyl complex.73-75 Activation energies of less than 10 kcal/mol are not unusual (especially for late transition me tals) and thus render th is reaction very common in the organometallic literature.76 In addition, metal complexe s bearing other ligands that contain hydrogen atoms in the -position can react in a similar manner allowing for alkyl-amido compounds to also be considered in this discussion. Although -hydrogen elimination reactions from non-alkyl complexes are generally slower due to higher activation energies, they have to be considered in this discussion.77,78 Figure 1-7 shows the classic reaction mechanisms for hydrogen elimination and -hydrogen abstraction from metal amido complexes. In classical organometallic chemistry, certain requirements need to be fulfilled for hydrogen elimination to occur. Besides the availability of a hydrogen atom in the -position, an empty metal orbital has to be accessible to accommodate the new metal-hydrogen bond. Additionally, both the metal center and the hydrogen atom in question need to be able to adopt a syn co-planar arrangement to allow for the transfer to occur at a reasonable rate.79 On the 26

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Figure 1-7. Mechanisms for -hydrogen elimination and -hydrogen abstraction. contrary, transfer of the hydrogen atom from its original position onto an adjacent amido ligand with concurrent rearrangement of bonds is characteristic of -hydrogen abstraction.80 This transformation is more common in coordinatively saturated complexes since an empty coordination site is not necessarily required. In either case, the result is the formation of an imine which in turn can be used to determine if a chemical reaction of this type occurred. A large number of ligands in CVD precursor systems have no or -hydrogen atoms but do have -hydrogens which can undergo -hydrogen abstraction to form metallacycles. Typically, metal alkyl complexes bearing alkyl groups such as ne opentyl are major candidates for participating in this type of transformation; however, under certain circumstances imido complexes with alkyl groups such as tert -butyl can exhibit similar reactivities as shown in Figure 1-8.81,82 In general, -hydrogen elimination can be considered a type of oxidative addition of a C-H bond to the metal center. However, in the case of alkylimido ligands, the abstraction can be seen as a net transfer of the -hydrogen to the -position creating an azam etallacyclobutane. 27

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Figure 1-8. Mechanism for -hydrogen abstraction. Typically, the M-N-C bond angle in alkyl-imido co mplexes is on the order of 180, not allowing for the appropriate overlap of metal orbitals with the C-H bond which is necessary for this reaction to occur. Therefore, the reaction is not favored when considering these geometric constraints which could explain the occurrence of this type of reaction only at elevated temperatures and/or in the pr esence of an activated surface ( vide infra ).83 In most precursor systems targeting metal nitride th in film deposition, the formation of metallacycles is undesirable since the strong M-C bond can lead to carbon contamination in th e produced films. Nevertheless, the byproducts of -hydrogen abstraction such as is obutylene are indicative of this type of precursor decomposition. -Alkyl elimination Migratory insertion of an al kene into a metal-alkyl bond is a well known mechanism which is commonly found in Ziegler-Natta polymer ization reactions i nvolving early metal d0 complexes.84 The microscopic reverse of this transformation, namely -alkyl elimination, constitutes a high energy intramolecular CC bond activation process which has been documented for both early and late transition metal complexes.85,86 During this rearrangement, an alkyl group is transferred from an existing alkyl-based ligand onto the metal center to form a new metal-alkyl bond which is depicted in Fi gure 1-9. Despite the high energy demand, the probability of an occurrence of this type of e limination reaction is greatly increased since the metal complexes are subjected to a high energy e nvironment inside a CVD reactor. Subsequent 28

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-alkyl eliminations can result in the formation of nitriles which can be a strong indicator for this type of mechanism.87,88 Figure 1-9. Mechanism for -alkyl elimination. Co-reactant induced decomposition Up to this point, only intramolecular deco mposition pathways have been discussed. During a typical CVD reaction, the activated subs trate surface and co-reactant gases possess the capability of opening new pathways for decomposition which would be inaccessible in solution based organometallic chemistry. Dangling bond s and open coordination sites on the substrate surface may act as receptors for hydrogen atoms, alkyl-groups or byproducts formed during the previously discussed decomposition mechanisms. Therefore, elimination reactions that would typically be impossible due to the lack of ope n coordination sites on the organometallic complex suddenly become feasible reac tion pathways. In addition, it has been shown by multiple researchers that CVD byproducts such as alkoxides and alkanes can undergo further decomposition on Si and GaAs surfaces through various reaction mechanisms.89-92 However, since the surface chemistry of organometallic compounds is extraordinarily complex, a comprehensive discussion of these phenomena is well beyond the scope of this document. Molecular hydrogen is a commonl y used co-reactant gas in th in film deposition. Besides its ability to assist in the re duction of the metal center, hydrogen can open up new pathways for the removal of metal-bound ligands. Co mputational studies by McElwee-White et al. suggest that relatively low-lying transi tion states (~37 kcal/mol) for -bond metathesis involving hydrogen and a tungsten-chlorine bond (from (CH3CN)Cl4W NR, where R = Ph, allyl, iPr) may 29

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account for the removal of halide atoms from the precursor.56 Besides the reactivity of hydrogen towards the precursor molecules themselves in the gas phase, surface-bound H-atoms may influence the decomposition pro cess by aiding the reaction of th e incoming precursor molecules with the substrate surface. On the contrar y, they may also block surface sites, therefore decelerating the film deposition process by surface passivation. High energy decomposition routes As mentioned before, the high energy e nvironment during a CVD process allows consideration of decomposition r outes that would be negligible in solution based chemistry. Homolysis of a metal-carbon bond in metal alkyl complexes can be considered a member of this family of reactions. The generation of metal and alkyl radicals duri ng M-C bond cleavage often constitutes high energy processes resulting in the formation of highly unstable species. Computational studies by Maejima et al. suggest that -hydrogen elimination (Ea = ~45 kcal/mol) is the preferred deco mposition pathway when compared to the homolysis of a Zn-Et bond (Ea = ~55 kcal/mol), however, homolysis cannot be entirely neglected especially when considering high temperature depositions.93 Furthermore, C-C and C-N bond ruptures are necessary to account for all the byproducts observed in a study performed by Nuzzo et al.94 Case Study: BTBTT and BTBDT The complexity of the decomposition of an or ganometallic precursor to its ceramic solid state product makes direct observation of reactiv e intermediates a daunting task. Two metal complexes for deposition of tungsten nitride (WNx) films, (tBuN)2W(NHtBu)2 (BTBTT) and (tBuN)2W(NEt2)2 (BTBDT), are among the few precursors that have received a considerable amount of effort towards understanding the deta ils of the decompositi on process. In the following paragraphs, a brief summary of the fi ndings from various research groups regarding 30

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these two compounds are presented in order to support the prev iously discussed mechanisms.87,88,94 Deposition of WNx Film from BTBTT In order to achieve a broad understanding of the BTBTT precursor and its behavior during deposition, investigations covered a temperature range from 100 to 850 K.87 Low temperature XPS investigations revealed that the precursor molecules adsorb to the substrate surface at 100 K without undergoing any chemical reactions. Thermal desorption spectrometry (TDS) measurements indicated the continuous evolution of tBuNH2 ( m/z = 58) from temperatures as low as 270 K up to 590 K thus confirming the thermal instability of the precursor molecules. Control experiments showed that amine desorp tion from the substrate surface saturated with tBuNH2 (no BTBTT present) ceased at 350 K, provi ng that the previously observed desorption product must originate from BTBTT molecules undergoing the -H abstraction mechanism described earlier (Figure 1-6). The lack of -H atoms in the precursor molecules renders -H abstraction the lowest energy transformation av ailable to this precursor; however, surface mediated N-H activation resulting in dispr oportionation and W-N(amido) bond cleavage could not be excluded as a source for tBuNH2 evolution. In either case, formation of the intermediate complex 15 was observed on the surface along with its corresponding dimer [(tBuN)2W( NtBu)]2 16. Both 15 and 16 were identified via the binding ener gies of tungsten and nitrogen in the XPS spectra (Figure 1-10). Figure 1-10. Formation of tBuNH2 from BTBTT via -H abstraction. 31

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With the aim of getting a better under standing of the kine tics involved in tBuNH2 formation, investigators attempte d to fit the experimental resu lts to traditio nal Arrhenius parameters following the hypothetical reaction sc heme illustrated in Figure 1-11A. Using a rough approximation, the precursor can adsorb re versibly to the substrate surface with an adsorption constant k1 and its microscopic reverse k-1. Upon adsorption, the activated precursor (denoted (tBuN)2W(NHtBu)2*) may decompose to form product (tBuNH2) with the reaction constant k2. Fitting the experimental data to traditi onal Arrhenius reaction ki netics results in a calculated activation energy for precursor desorption Edesorb of roughly 21 kcal/mol, which is in good agreement with the activation energy for sub limation of the parent compound. Fitting the data to the equation for product formation provi des an activation energy of ~33 kcal/mol. Figure 1-11. Reaction kinetic s of BTBTT decomposition. Upon raising the temperature, two broad peaks were evident in the TDS profile at 515 and 575 K, corresponding to a m/z = 56 fragment, which were attri buted to isobutylene originating from -hydrogen elimination reactions. Figure 1-12 depicts a possible reaction mechanism for the evolution of isobutylene from 15. The authors noted that th e W-N-C bond angles (~180) of the imido moiety might render involvement of th e substrate surface necessary for cleavage to isobutylene. However, the resulting intermediates would be identical to -hydrogen elimination products, which in turn render identification of the exact decomposition mechanism difficult. Furthermore, it was noted that reactive intermediates such as 17 may be responsible for the observed evolution of NH3 through reaction with H-atoms on the substrate surface. 32

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Figure 1-12. Formation of isobutylene from 15 via -H abstraction. During the same temperature ra nge, evolution of acetonitrile ( m/z = 41) was observed, which is consistent with the aforementioned possibility of multiple -methyl abstraction reactions. The authors noted that besides the partially decomposed tungsten complex, which can accept the abstracted methyl groups, the substrate surface is likely to play a major role as an accepting moiety as well since the W-N-C bond angles of 15 (~180) are again not favorable for methyl abstraction. Some possible products of -methyl abstraction from 15 are shown in Figure 1-13. Figure 1-13. Formation of acetontrile from 15 via successive -methyl abstractions. Again, the reactive scattering waveform of the m/z = 41 fragment was investigated by fitting the obtained data to simplified theoretical models. Since this reaction takes place after precursor adsorption to the substrate has alrea dy occurred and can ther efore be considered irreversible, a simplified mechanistic model (Fig ure 1-11B) was chosen re sulting in a calculated activation energy of ~43 kcal/mol. Because this decomposition is most likely a complex process which is poorly described by these crude approximations, a distinction between -H abstraction and -methyl elimination is not possible. 33

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Besides the occurrence of or ganic byproducts which can be explained through standard organometallic decomposition reactions, other gaseous products were detected in the reactor effluent when H2 carrier gas was employed. The author s explain the formation of hydrogen cyanide (HCN) via possible decomposition of acetonitrile on the substrate surface and subsequent recombination of cyanide with H-atoms. Similar reasoning may explain the formation of methane by reac tion of methyl groups with surface-bound H-atoms. The rising baseline in the temperature programmed reac tion spectroscopy (TPRS) spectra at higher temperatures is due to desorption of N2 gas as a result of diffusion of N atoms out of the bulk WNx layer. This phenomenon, also known as ni trogen volatilization, has been observed in multiple investigations of tungsten nitride and may be responsible for the low N/W ratios seen in high temperature depositions.95-98 Also contributing to the byproduct flux is desorption of H2 gas from the surface at >600 K as a result of reco mbination of surface-bound H-atoms. Flattening of the TPRS spectra at temperatur es in excess of 700 K indicate th at the reaction is entering the mass transport controlled regime. Although most of the organic byproducts can be explained by standard organometallic concepts, the final decomposition of W containing species to form WNx films with specific stoichiometries remains unexplained. Ruth erford backscattering spectroscopy (RBS) experiments revealed that the onset of complete precursor decompos ition may be found at temperatures in excess of 500 K. The most impo rtant reactive intermediate for depositions from BTBTT is postulated to be the tris-imido species 15, due to its high abunda nce in the gas phase desorption products. The ultimate fate of this key species is still unc ertain; however, similar species have been observed in closely related osmium and rhenium systems.99,100 These findings imply that film growth is ultimately limited by reactions involving extensive C-N, C-C and C-H 34

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bond ruptures of the surface-bound amido/imido species The energies required to activate these pathways are sufficiently high to compete with N2 and H2 extrusion which in turn render identification of further intermediates difficult with this array of availabl e spectroscopic tools. This assumption is supported by the absence of extensive C and H contamination in the WNx films deposited from BTBTT (WN1.5C0.4O0.1) which would be expected if surface-bound amines and alkyl-groups were incorporated into the depo sited films. Additionally the mechanistic steps occurring during the tran sition of monomeric precursor speci es towards the cubic WN lattice continue to defy explanation. Nevertheless, the aut hors speculate that th e precursor molecules oligomerize in the initial stages of decomposition to form stru ctures analogous to that of W4N4(NPh2)6(OC4H9)2 20 (Figure 1-14).101 This molecule possesses an intriguing W4N4 core (two 2-N atoms and two 3-N atoms) that would result in th e formation of a cubic WN lattice upon 3-dimensional addition of WN units. Figure 1-14. Structure of 20 with a W4N4 skeleton. Depositions from BTBDT Film depositions from BTBDT 21 were studied using an anal ogous range of spectroscopic tools and similar temperature conditions. Noticeable differences from depositions from BTBTT 7 were observed at low temperatures. The presence of -H atoms in BTBDT allows for low temperature decomposition pathways which were not accessible in the previously discussed system. Consequently, a different set of byproducts were observed in the TDS spectra resulting 35

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from reactions involving the diethyl amido ligand. Dissociation of HNEt2 at low temperatures (<300 K) suggests th e occurrence of -H abstraction reactions, which would be accompanied by formation of reactive intermediate 22 (and the corresponding resonance structure 23 ) containing the coordinated imine species EtN=CHCH3 (Figure 1-15). No definitive assignments of the peaks in the XPS spectra could be made, but at slightly higher temperatures (<470 K), decomposition of 21 resulting in desorption of EtN=CHCH3 ( m/z = 71) from the surface provided evidence for the occurrence of this -H elimination pathway. Figure 1-15. Formation of EtN=CHCH3 from BTBDT via -H elimination. Following -H elimination and dissociation of EtN=CHCH3, the remaining W-containing intermediate is similar to the detected species during deposition from BTB TT. Therefore, further decomposition pathways such as -H elimination involving the tBu-imido ligands follow similar reaction schemes as discussed previously. Thus high temperature deposition byproducts such as HCN and CH3CN were almost identical to the ones s een for BTBTT with only minor differences in the exact temperature ranges. Conclusions As observed throughout the case studies of BTBTT and BTBDT, a carefully designed array of spectroscopic tools in combination with understanding of organome tallic principles can yield great insight into precursor decom position pathways during thin film deposition. Nonetheless, a large portion of the deposition process is still poor ly understood, requiring additional research to be conduc ted. The transition from monomeric intermediates towards 36

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37 formation of the final material layer is poorly understood and requires clarification in order to make thin film depositions more predictable. The following chapters describe the synt hesis of new diorganohydrazido(2-) tungsten complexes and their subsequent use as single-source precursors for the deposition of WNxCy thin films. The compounds are characterized by a variety of spectroscopic methods to confirm their identity as well as their struct ural features. Depositions of WNxCy films are described and their properties as Cu diffusion barriers are investigated.

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CHAPTER 2 SYNTHESIS AND CHARACTERIZATION OF DIORGANOHYDRAZIDO(2-) TUNGSTEN COMPLEXES Diorganohydrazido(2-) Complexes of Early Transition Metals Early transition metal complexes of diorganohyd razido(2-) ligands have appeared in the literature since the 1970s. Especi ally hydrazido complexes of group 6 metals such as Mo and W are quite well investigated due to th eir importance as model compounds for N2 fixation.102-106 Hence, a variety of complexes featuring unsubstitu ted and/or alkylated hy drazines with different coordination modes (mono or dianio nic) are known such as [Cp*WMe3( 2-NH2NH2)][OTf],107 [W(N-2,6-iPr2C6H3)(2,6-NC5H3(CH2NTosyl)2( 2-NHNH2)],108 [W(NNPhMe)Cl3(PMe3)2],109 and [(HIPTN3N)Mo(NNH2)][Ar4B].110,111 However, the synthesis of tungsten hydrazido compounds for use in MOCVD of WNx and WNxCy films is poorly investigated. In the following paragraphs, the synthesis and ch aracterization of a new family of diorganohydrazido(2-) tungsten complexes is described. Synthesis of Diorganohydrazido(2-) Tungsten Complexes The tungsten hydrazido complexes 24 27 were prepared by reacting the corresponding 1,1-diorganohydrazine with WCl6 in methylene chloride at -78 C (Figure 2-1). The resulting Cl-bridged tungsten dimer was not isolated but was subsequently treate d with acetonitrile or pyridine to yield compounds 24 27 as orange, rust colored, purpl e and red solids, respectively. The ability to prepare these products in batch sizes of up to five grams with similar yields (with the exception of compound 27) is an advantage since a comp lete set of CVD experiments requires roughly two grams of material. 1H and 13C NMR spectra are in good agreement with the symmetry equivalence of the substituents on the hydrazido functi onality in compounds 24 and 25. Contrary to this finding, NMR spectra reveal the inequivalence of the two phenyl rings in compounds 26 and 27. Two sets of peaks are visible in the aryl region indicating that rotation 38

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around the N-C bond of the hydrazido functionality is slow on the NMR timescale which is most likely a result of the steric demand of the two phenyl rings. Figure 2-1. Synthesis of compounds 24 27. X-Ray Crystallography Study Single crystals suitable for X-ray di ffraction were obtained from compounds 24 27 and their structures were determined. Compounds 24 and 25 adopt a pseudo-octah edral geometry as shown in the ORTEP representations depicted in Figures 2-3 and 2-4, respectively. The tungsten-chlorine bond distances ar e on the order of 2.34 which is within the expected range for tungsten(VI)-chlorine bonds.112 The short W(1)-N(1) bo nd distance (1.769(5) ) of compound 24 and a short bond distance of 1.271(8) be tween N(1) and N(2) suggests a high degree of delocalization and significant multip le bond character throughout the W(1)-N(1)-N(2) unit, which is consistent with other hydrazido complexes of tungsten with multiple chloride ligands such as [W( 5-C5Me5)Cl3(NNPh2)]113 (W-N 1.769(2) N-N 1.296(3) ) and cis [WCl3(NNH2)(PMe2Ph)2]114 (W-N 1.752(10) NN 1.300(17) ). Compound 25 displays similar bond lengths (W(1)-N(1) 1.752(3) N(1)-N(2) 1.265(4) ) suggesting a similar bonding situation. This observation can be explained based upon two possible limiting electronic structures A and B shown in Figure 2-2, with repr esentation A being the major 39

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contributor for both compounds 24 and 25. In addition, the piperidyl unit of 25 can be found in a typical chair-like conformation with the C(1)-C(5 )-N(2)-N(1) unit exhibiti ng a trigonal planar arrangement as evidenced by the sum of the bond angles (359.7) around N(2). Furthermore, the W(1)-N(3) bond distances of 2.224(7) for 24 and 2.237(3) for 25 are significantly shorter than those reported for related tungste n imido compounds, suggesting a decreased trans influence of the diorganohydrazido(2-) li gand compared to the imido moiety.55 Selected bond lengths and angles for 24 and 25 are given in Table 21 and 2-2, respectively. Figure 2-2. Possible resonance structur es of diorganohydrazido(2-) complexes. The structures of compounds 26 and 27 show similarities to those of compounds 24 and 25. Complexes 26 and 27 also exhibit pseudo-octahedral geom etry at the tungsten center as seen in Figures 2-5 and 2-6, respectively. Howeve r, W(1)-N(1) bond dist ances of 1.742(4) and 1.739(5) and N(1)-N(2) distances of 1.312(5) and 1.311(6) for 26 and 27, respectively, suggest less conjugation thr oughout the hydrazido moiety as compared to compounds 24 and 25. One hydrazido phenyl ring is coplanar with the N(2)-N(1)-W(1) unit, maximizing the conjugation between the two subunits, as has been observed for othe r 1,1-diphenylhydrazido complexes of tungsten.115 This additional mode of conjugation decreases the electron density between N(1) and N(2), resulting in a noteworthy elongation of the N-N bond. In addition, the slightly shorter W-N bond suggests higher -bonding character such that compounds 26 and 27 40

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experience a greater contribution from resonance structure B (Figure 2-2) The large N-W-Cl bond angles in both compounds reflect the increased steric demand of the coplanar phenyl ring. Selected bond lengths and angles for 26 and 27 are given in Tables 23 and 2-4, respectively. Crystal data and structure refinement for these complexes can be found in Table 2-5. Table 2-1. Selected bond dist ances () and angles () for 24. Bond Bond Length () Bond Bond Angle () W1-N1 1.769(5) N1-W1-N3 180.000(1) W1-N3 2.224(7) N1-W1-Cl1 96.85(4) W1-Cl1 2.3374(16) N3-W1-Cl1 83.15(4) W1-Cl2 2.3562(16) N1-W1-Cl2 95.02(3) N1-N2 1.271(8) N3-W1-Cl2 84.98(3) N2-C1 1.438(7) Cl1-W1-Cl2 89.25(7) N2-N1-W1 180.0 N1-N2-C1 119.1(4) C1-N2-C1A 121.9(7) Table 2-2. Selected bond dist ances () and angles () for 25. Bond Bond Length () Bond Bond Angle () W1-N1 1.752(3) N1-W1-N3 178.24(11) W1-N3 2.237(3) N1-W1-Cl1 92.03(9) W1-Cl1 2.3609(9) N3-W1-Cl1 86.68(8) W1-Cl2 2.3252(8) N1-W1-Cl2 96.70(8) W1-Cl3 2.3563(9) N3-W1-Cl2 82.11(7) W1-Cl4 2.3444(8) Cl1-W1-Cl2 90.33(3) N1-N2 1.265(4) N2-N1-W1 176.6(3) N2-C1 1.461(4) N1-N2-C1 120.7(2) N2-C5 1.473(4) C1-N2-C5 118.7(3) Table 2-3. Selected bond dist ances () and angles () for 26. Bond Bond Length () Bond Bond Angle () W1-N1 1.742(4) N1-W1-N3 174.91(14) W1-N3 2.216(4) N1-W1-Cl1 96.58(11) W1-Cl1 2.3191(11) N1-W1-Cl2 99.15(11) W1-Cl2 2.3445(11) N1-W1-Cl3 98.02(11) W1-Cl3 2.3519(11) N1-W1-Cl4 91.80(11) W1-Cl4 2.3537(11) N2-N1-W1 169.8(3) N1-N2 1.312(5) N1-N2-C1 115.0(4) N2-C1 1.447(5) N1-N2-C7 120.7(3) N2-C7 1.429(6) C1-N2-C7 123.6(4) 41

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Table 2-4. Selected bond dist ances () and angles () for 27. Bond Bond Length () Bond Bond Angle () W1-N1 1.739(5) N1-W1-N3 179.13(17) W1-N3 2.307(4) N1-W1-Cl1 94.20(14) W1-Cl1 2.3375(13) N1-W1-Cl2 95.30(14) W1-Cl2 2.3564(12) N1-W1-Cl3 95.55(14) W1-Cl3 2.3525(13) N1-W1-Cl4 96.94(13) W1-Cl4 2.3224(12) N2-N1-W1 175.7(4) N1-N2 1.311(6) N1-N2-C1 116.8(4) N2-C1 1.450(6) N1-N2-C7 120.0(4) N2-C7 1.421(6) C1-N2-C7 123.2(5) Figure 2-3. Thermal ellipsoids diag ram of the molecular structure of 24. Thermal ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity. 42

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Figure 2-4. Thermal ellipsoids diag ram of the molecular structure of 25. Thermal ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity. 43

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Figure 2-5. Thermal ellipsoids diag ram of the molecular structure of 26. Thermal ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity. 44

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45 Figure 2-6. Thermal ellipsoids diag ram of the molecular structure of 27. Thermal ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity.

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Table 2-5. Crystal data and stru cture refinement for compounds 24 27. 24 25 26 27 Empirical formula C4H9Cl4N3W C7H13Cl4N3W C28H26Cl8N6W2 C17H15Cl4N3W Formula weight 424.79 464.85 1097.85 586.97 Temperature (K) 173(2) 173(2) 173(2) 173(2) Wavelength () 0.71073 0.71073 0.71073 0.71073 Crystal system Monoclinic M onoclinic Monoclin ic Monoclinic Space group C2/c P21/n P21/n P21/c Unit cell dimensions a = 8.7700(7) a = 9.7113(15) a = 10.8288(8) a = 9.1520(12) b = 13.8203(11) b = 14.874(2) b = 17.8753(13) b = 9.5011(12) c = 9.7343(8) c = 9.7939(15) c = 18.2409(13) c = 22.491(3) = 90 = 90 = 90 = 90 = 100.575(2) = 92.777(3) = 101.006(1) = 100.400(2) = 90 = 90 = 90 = 90 Volume (3) 1159.80(16) 1413.0(4) 3465.9(4) 1923.6(4) Z 4 4 4 4 Density (Mg/m3) 2.433 2.185 2.104 2.027 Absorption coefficient (mm-1) 10.837 8.906 7.280 6.566 F ( 000 ) 784 872 2080 1120 Crystal size (mm3) 0.19 x 0.15 x 0.08 0.19 x 0.11 x 0.02 0.12 x 0.11 x 0.04 0.21 x 0.08 x 0.05 Theta range for data collection () 2.78 to 27.49 2.49 to 27.50 1.61 to 27.50 1.84 to 27.50 Index ranges -8 h 11 -10 h 12 -14 h 13 -9 h 11 -17 k 15 -19 k 17 -22 k 23 -12 k 12 -12 l 11 -12 l 9 -21 l 23 -26 l 29 Reflections collected 3683 9391 23178 12705 Independent reflections (Rin t ) 1333 (0.1092) 3245 (0.0546) 7931 (0.0559) 4383 (0.0940) Completeness to = 24.60 (%) 99.4 99.9 99.7 99.3 Absorption correction Integration In tegration Integration Integration Max. and min. transmission 0.5020 and 0.1814 0.8420 and 0.2825 0.7594 and 0.4754 0.7446 and 0.3434 Refinement method Full-matrix L.S. on F2 Full-matrix L.S. on F2 Full-matrix L.S. on F2 Full-matrix L.S. on F2 Data / restraints / parameters 1333 / 0 / 60 3245 / 0 / 137 7931 / 0 / 399 4383 / 0 / 226 Goodness-of-fit on F2 1.027 1.155 0.961 0.888 46

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47Table 2-5. continued. R1a 0.0325 0.0203 0.0274 0.0319 wR2 b 0.0793 0.0541 0.0584 0.0694 Largest diff. peak and hole/e3 4.084 and -1.814 1.309 and -1.035 1.264 and -0.947 1.588 and -2.129 R1 = (||Fo| |Fc||) / |Fo| wR2 = [ [w(Fo 2 Fc 2)2] / [w(Fo 2)2]]1/2 S = [ [w(Fo 2 Fc 2)2] / (n-p)]1/2 w = 1/[ 2(Fo 2)+(m*p)2+n*p] p = [max(Fo 2,0)+ 2* Fc 2]/3 m & n are constants.

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Thermogravimetric Analysis The thermal behavior of compounds 24 26 was investigated as pr eliminary screening for use of complexes 24 27 as precursors for the MOCVD of WNxCy. Thermogravimetric analysis (TGA) experiments were run at a heating rate of 10 C/min from 50 to 900 C. The TGA curves of 24 and 25 show residual masses of 58 and 50%, re spectively, which are constant above 550 C (Figure 2-7). Compound 26 shows continuous mass loss even at the end of the temperature range indicating more complicated decomposition be havior possibly due to the relatively large mass of the two phenyl rings. In all cases, how ever, an initial drop in mass of about 10% is observed corresponding to loss of the acetonitrile lig and. Since this dissociation is observed in the low temperature range, it can be assumed that the acetonitrile is bound weakly to the tungsten metal center. 40% 50% 60% 70% 80% 90% 100% 50 250 450 650 850Weight%Temperature (oC) 24 25 26Figure 2-7. TGA curve of compounds 24 26 recorded at a heating rate of 10 C/min under nitrogen. Nuclear Magnetic Resonance Spectroscopy Investigation To corroborate the findings from the TGA analysis, the kinetics of acetonitrile exchange were determined via NMR spectroscopy. The sample for the exchange study was prepared in the 48

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glovebox by dissolving complex 24 and an approximately equivale nt amount of acetonitrile in toluene-d8. The 1H spectrum of this sample at 40 C displayed the signals for 24 at 0.53 ppm and acetonitrile at 0.83 ppm, in a ratio 1 : 2.09. The exchange of 24 with acetonitrile was monitored by 1H NMR in a temperature range from 40 to 84 C The exchange rate k was determined by line shape analysis in the temperature interval 50 to 84 C. A plot of ln(k/T) vs. 1/T (Figure 2-8) in the temperature interval from 50 to 84 C afforded an activation enthalpy of 23.0 kcal/mol and an activation entropy of 28.8 cal/molK, consis tent with dissociat ive exchange. The corresponding Gibbs free energy of activation is 14.4 kcal/mol, i ndicating a relativ ely weak W-N bond that should break easily under CVD conditions. R = 0.9985 4 3 2 1 0 0.002780.002830.002880.002930.002980.003030.00308ln(k/T)1/T 1/T vs. ln(k/T) regression lineFigure 2-8. Plot of ln(k/T) vs. 1/T for acetonitrile exchange in complex 24 Mass Spectrometry Since a correlation between the mass spectrome tric fragmentation patterns of precursors and likely decomposition pathways during CVD has been postulated in the literature,55,116,117 mass spectra were obtained from compounds 24 26. Although care has to be taken when 49

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comparing chemical ionization with therma l degradation occurring during CVD reactions, fragmentation patterns allow some insight into structural we aknesses of the compounds under investigation. Table 2-6 summarizes the major fr agment ions observed in the positive ion CI (chemical ionization) spectra of compounds 24 26. No molecular ion peak was observed in the CI spectra of 24, 25 or 26, consistent with facile loss of th e acetonitrile ligand. Instead, the highest m/z values were in mass envelopes at 384, 354 and 508, corresponding to [Cl4W(NNMe2)]+, [Cl2W(HN-pip)]+ and [Cl4W(NNPh2)]+, respectively. The base peak in the CI spectrum of 24 was observed at m/z 349, corresponding to the [Cl3W(NNMe2)]+ fragment. Interestingly, the base peaks in the CI spectra of 25 and 26 at m/z 84 and 170, corresponding to the [pip]+ and [Ph2NH2]+ fragments, respectively, are indi cative of the hydrazido N-N bond being broken under ionization conditions, which is add itionally supported by the presence of the [Cl3WNH2]+ fragment in the CI spectrum of 26 at m/z 307. Cleavage of the N-N bond would also be on the pathway for decomposition of 25 and 26 to WNx films under CVD conditions. Table 2-6. Summary of relative abundances for positive ion CI mass spectra of compounds 24 26. Compound CI Fragments m/z abundancea 24 [Cl4W(NNMe2)]+ 384 8 [Cl3W(NNMe2)]+ 349 100 [Cl3W]+ 289 4 25 [Cl2W(HN-pip)]+ 354 30 [Cl3W]+ 289 12 [Me2pip]+ 114 18 [H2pip]+ 86 70 [pip]+ 84 100 26 [Cl4W(NNPh2)]+ 508 5 [Cl3W(NNPh2)H]+ 473 21 [Cl3WNH2]+ 307 4 [Ph2NMe2]+ 198 19 [Ph2NH2]+ 170 100 a Relative abundances were adjusted by summing the observed intensities fo r the predicted peaks of each mass envelope and normalizing the largest sum to 100%. 50

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Experimental Procedures and Syntheses General Procedures Unless specified otherwise, all manipulations were performed under an inert atmosphere (N2) using standard Schlenk or glovebox techniques All reaction solvents were purified using an MBraun MB-SP solvent purification system pr ior to use. NMR solvents were degassed by three freeze-pump-thaw cycles and stored over 4 molecular sieves in an inert atmosphere glovebox. 1H and 13C NMR spectra were recorded on Gemini 300, Mercury 300 or VXR 300 spectrometers using residual protons of deuterated solvents for reference. Pentane, pyridine, acetonitrile and benzonitrile (all anhydrous) were used as received from Aldrich. 1,1Dimethylhydrazine, 1,1-diphenylhyd razine and 1-aminopiperidine were degassed by three freeze-pump-thaw cycles and stored over 4 molecular sieves. All other chemicals were used as received without further purification. Synthesis of (CH3CN)Cl4WNNMe2 (24) A Schlenk flask was charged with WCl6 (2.10 g, 5.30 mmol) and 40 mL of methylene chloride. 1,1-Dimethylhydrazi ne (0.39 mL, 5.2 mmol) was a dded via syringe under vigorous stirring at -78 C. After 10 min of stirring, the solvent was removed in vacuo while warming to room temperature. Acetonitrile (15 mL) was added via syringe and the mixture was stirred for an additional 30 min. The solvent was removed in vacuo and the solid extracted with 2 x 15 mL of methylene chloride. The combined extracts were filtered and the volume reduced to 15 mL. The product was precipitated by adding the solution into vigorously stirre d pentane (200 mL) at 0 C. The orange product was filtered off as a microcrystalline powder and dried in vacuo Yield 1.66 g (75%, 3.92 mmol). 1H NMR (benzene-d6, 25C): 5.35 (s, 6H, N(C H3)2), 0.15 (s, 3H, C H3CN). 13C NMR (benzene-d6, 25C): 0.58 ( C H3CN), 36.89 (N( C H3)2), 120.86 51

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(CH3C N). Anal. Calcd. for C4H9Cl4N3W: C, 11.31; H, 2.14; N, 9.89. Found: C, 10.89; H, 1.97; N, 9.52. Synthesis of (CH3CN)Cl4WN-pip (25) A Schlenk flask was charged with WCl6 (2.00 g, 5.04 mmol) and 40 mL of methylene chloride. 1-Aminopiperidine (0.53 mL, 4.9 mmol ) was added via syringe under vigorous stirring at -78 C. After 10 min of stirring, the solvent was removed in vacuo while warming to room temperature. Acetonitrile (15 mL) was added vi a syringe and the mixture was stirred for an additional 30 min. The solvent was removed in vacuo and the solid extracte d with 2 x 20 mL of methylene chloride. The extract was filtered and the volume reduced to 15 mL. The product was precipitated by adding the methylene chloride solution into vigorously stirred pentane (200 mL) at 0 C. The rust-colored product was filtered off as a microcrystalline powder and dried in vacuo Yield 1.75 g (76%, 3.76 mmol). 1H NMR (benzene-d6, 25C): 4.86 (t, 4H, NC H2), 1.34 (m, 4H, C H2), 1.01 (m, 2H, C H2), 0.17 (s, 3H, C H3CN). 13C NMR (benzene-d6, 25C): 0.75 ( C H3CN), 22.73 ( C H2), 30.70 ( C H2), 51.00 (N C H2), 120.78 (CH3C N). Synthesis of (CH3CN)Cl4WNNPh2 (26) A Schlenk flask was charged with WCl6 (2.00 g, 5.04 mmol) and 40 mL of methylene chloride. 1,1-Diphenylhydrazine (0.91 g, 4.9 mmol) was added via syringe under vigorous stirring at -78 C. After 10 min of stirring, the solvent was removed in vacuo while warming to room temperature. Acetonitrile (15 mL) was added via syringe and the mixture was stirred for an additional 30 min. The solvent was removed in vacuo and the solid extracted with 2 x 20 mL of methylene chloride. The combined extracts were filtered and the volume reduced to 15 mL. The product was precipitated by adding the solution into vigorously stirre d pentane (200 mL) at 0 C. The deep purple product was filtered off as a microcrystalline powder and dried in vacuo Yield 2.07 g (76%, 3.77 mmol). 1H NMR (benzene-d6, 25C): 7.15 (broad s, 8H, Ph), 6.5352

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6.47 (m, 2H, Ph), 0.11 (s, 3H, C H3CN). 13C NMR (benzene-d6, 25C): 0.97 ( C H3CN), 121.23 (CH3C N), 125.65 (Ph), 125.77 (Ph), 128.80 (Ph), 128.94 (Ph), 130.53 (Ph), 130.65 (Ph), 131.39 (Ph), 131.61 (Ph), 133.38 ( Cipso), 135.34 ( Cipso). Synthesis of (py)Cl4W NNPh2 (27) A Schlenk flask was charged with WCl6 (2.00 g, 5.04 mmol) and 40 mL of methylene chloride. 1,1-Diphenylhydrazine (0.91 g, 4.94 mmol) was added via syringe under vigorous stirring at -78 C. After 10 min of stirring, the solvent was removed in vacuo while warming to room temperature. Pyridine (15 mL) was added via syringe and the mixture was stirred for an additional 30 min. The solvent was removed in vacuo and the solid extracte d with 2 x 30 mL of benzene. The combined extracts were filtered and the solvent removed in vacuo to afford 27 in 27% yield as a dark red microcry stalline solid (0.81 g, 1.38 mmol). 1H NMR (benzene-d6, 25C): 9.58-9.55 (m, 2H), 7.19-7.11 (m, 10H), 6.68-6.36 (m, 3H). 13C NMR (benzene-d6, 25C): 118.56, 121.51, 124.02, 124.73, 125.98, 128.86, 128.91, 129.89, 130.67, 133.46, 139.32, 143.95, 152.91. Anal. Calcd. for C17H15Cl4N3W: C, 34.79; H, 2.58; N, 7.16. Found: C, 34.60; H, 2.31; N, 6.96. NMR Spectroscopy 1H NMR spectra for kinetic studi es were recorded on a Varian Inova spectrometer at a frequency of 500 MHz, on a 5 mm indirect detect ion probe. The variable temperature spectra were recorded on automation. To achieve temper ature stability, for each temperature step of 2 C a preacquisition delay of 1200 s was followed by shimming on the lock level. The spectra were collected in 64 transients, with an acquisition time of 5 s. No relaxation delay and no apodization were used. The simulation of th e spectra was done using the gNMR program.118 53

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Thermogravimetric Analysis TGA analysis was carried out using a Perkin-Elmer TGA7 thermogravimetric analyzer under nitrogen with a heating rate of 10 C/min (sample size 3 mg). Mass Spectrometry All mass spectral analyses were performed using a ThermoScientific DSQ (quadrupole MS) mass spectrometer (Thermo Finnigan, San Jose, CA) equipped with a di rect insertion probe (DIP) that was held at 50 C for 1 minute and then heated up to 280 C at 30 /min during the sample analysis. Ion source temperature wa s 150 C with methane gas at 0.5 mL/min. Crystallographic Studies X-ray data collection and structure refinement for 24 Data were collected at 173 K on a Siemens SMART PLATFORM equipped with a CCD area detector and a graphite monochromator utilizing MoK radiation ( = 0.71073 ). Cell parameters were refined using up to 8192 reflections. A full sphe re of data (1850 frames) was collected using the -scan method (0.3 frame width). The first 50 frames were re-measured at the end of data collection to monitor instrument and crystal stability (maximum correction on I was <1 %). Absorption corrections by integrat ion were applied based on measured indexed crystal faces. The structure of 24 was solved by the Direct Methods in SHELXTL6 ,119 and refined using full-matrix least squares. The non-H atoms were treated anisotropicall y, whereas the hydrogen atoms were calculated in ideal po sitions and were riding on their respective carbon atoms. The molecules are located on 2-fold rotation axes. A to tal of 60 parameters were refined in the final cycle of refinement using 1228 reflections with I >2 (I) to yield R1 and wR2 of 3.25% and 7.93%, respectively. Refinement was done using F2. A complete list of bond lengths, bond 54

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angles, atomic coordinates of non-H atoms and thermal parameters of 24 can be found in Tables A-1 A-3 of the Appendix. X-ray data collection and structure refinement for 25 Data were collected at 173 K on a Siemens SMART PLATFORM equipped with a CCD area detector and a graphite monochromator utilizing MoK radiation ( = 0.71073 ). Cell parameters were refined using up to 8192 reflections. A full sphe re of data (1850 frames) was collected using the -scan method (0.3 frame width). The first 50 frames were re-measured at the end of data collection to monitor instrument and crystal stability (maximum correction on I was <1 %). Absorption corrections by integrat ion were applied based on measured indexed crystal faces. The structure of 25 was solved by the Direct Methods in SHELXTL6 and refined using full-matrix least squares. The non-H atoms were treated anisotropicall y, whereas the hydrogen atoms were calculated in ideal positions and were riding on their respective carbon atoms. A total of 137 parameters were refined in the final cycle of refinement using 2948 reflections with I >2 (I) to yield R1 and wR2 of 2.03% and 5.41%, respectively. Refinement was done using F2. A complete list of bond lengths, bond angles, at omic coordinates of non-H atoms and thermal parameters of 25 can be found in Tables A-4 A-6 of the Appendix. X-ray data collection and structure refinement for 26 Data were collected at 173 K on a Siemens SMART PLATFORM equipped with a CCD area detector and a graphite monochromator utilizing MoK radiation ( = 0.71073 ). Cell parameters were refined using up to 8192 reflections. A full sphe re of data (1850 frames) was collected using the -scan method (0.3 frame width). The first 50 frames were re-measured at the end of data collection to monitor instrument and crystal stability (maximum correction on I 55

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was <1 %). Absorption corrections by integrat ion were applied based on measured indexed crystal faces. The structure of 26 was solved by the Direct Methods in SHELXTL6 and refined using full-matrix least squares. The non-H atoms were treated anisotropicall y, whereas the hydrogen atoms were calculated in ideal positions and were riding on their respective carbon atoms. The highest electron density peak in the final Difference Fourier map is most likely a result of a small disorder in one of the phenyl rings. The diso rder could not be resolved. A total of 399 parameters were refined in the final cycle of refinement using 6166 reflections with I >2 (I) to yield R1 and wR2 of 2.74% and 5.84%, respectively. Refinement was done using F2. A complete list of bond lengths, bond angles, atom ic coordinates of non-H atoms and thermal parameters of 26 can be found in Tables A-7 A-9 of the Appendix. X-ray data collection and structure refinement for 27 Data were collected at 173 K on a Siemens SMART PLATFORM equipped with a CCD area detector and a graphite monochromator utilizing MoK radiation ( = 0.71073 ). Cell parameters were refined using up to 8192 reflections. A full sphe re of data (1850 frames) was collected using the -scan method (0.3 frame width). The first 50 frames were re-measured at the end of data collection to monitor instrument and crystal stability (maximum correction on I was <1 %). Absorption corrections by integrat ion were applied based on measured indexed crystal faces. The structure of 27 was solved by the Direct Methods in SHELXTL6 and refined using full-matrix least squares. The non-H atoms were treated anisotropicall y, whereas the hydrogen atoms were calculated in ideal positions and were riding on their respective carbon atoms. A total of 226 parameters were refined in the final cycle of refinement using 3285 reflections with I 56

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57 >2 (I) to yield R1 and wR2 of 3.19% and 6.94%, respectively. Refinement was done using F2. A complete list of bond lengths, bond angles, at omic coordinates of non-H atoms and thermal parameters of 27 can be found in Tables A-10 A-12 of the Appendix.

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CHAPTER 3 METAL-ORGANIC CHEMICAL VAPOR DEPOSITION OF WNXCY THIN FILMS Film Growth and CVD Reactor Design Compounds 24 26 were subjected to CVD experiments in order to grow WNxCy thin films. To overcome volatility issues, the precursors were dissolved in benzonitrile with the precursor solution subsequently be ing injected (via a gastight syringe) into the nebulizer system attached to the CVD reactor. The generated aerosol was transported through a heated transfer tube into the reaction chamber via an impinging jet (Figure 3-1). Hydrogen was used as the carrier gas in all depositions a nd the reaction time was fixed at 150 min to allow for comparison of the acquired data such as f ilm thickness and growth rates. Figure 3-1. Schematic diagram of the CVD reactor.120,121 The actual deposition of thin films took pl ace on p-type boron doped Si (100) substrate wafers resting on a graphite susceptor which was inductively heated to the desired temperature 58

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by radio frequency (RF) coils. Depositions were typically carried out in a temperature range from 300 to 700 C under reduced pressure wh ich was maintained by mechanical roughing pumps. After completion of each run, the substrate wafers were removed from the reaction chamber and subjected to a series of characterization experiments. Characterization Techniques Film crystallinity was examined by X-ray diffraction (XRD) using Cu K radiation. Film composition was determined by Auger electron spectroscopy (AES) or XPS after cleaning the sample surface by sputter etching for 30 sec (AES) or 15 min (XPS) using Ar+ ions. The film thickness was measured by cross-se ctional scanning electron microscopy (X-SEM), whereas the sheet resistance of the deposited films was measured via 4-point probe. To test diffusion barrier quality, the WNxCy films were transferred to a sputter deposition system where 100 nm thick PVD Cu films were deposited foll owed by annealing of the Cu/WNxCy/Si stacks and subsequent AES or XPS depth profiling experiments. Alternatively, transmission electron microscopy (TEM) images were obtained from the tri-stack cross-sections in combination with energy dispersive spectroscopy (EDS) measurements to evaluate the barrier performance. Film Depositions from 24, 25, and 261 When CVD growth from 24 was attempted at 400 C in an inert atmosphere with N2 carrier gas, the resulting film contained W and O while no C or N was detected by AES. On the contrary, when H2 was substituted as the carrier gas for N2 at the same deposition temperature, the deposited films contained W, N, C, and O as determined by AES, indicating that H2 is crucial for successful film deposition from 24. The lowest temperature at which film growth was observed for 24 with H2 as a co-reactant was 300 C. WNxCy films deposited from 24 typically 1 Film depositions and characterizations performed by Dr. Hiral M. Ajmera and Dojun Kim. 59

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had the occurrence of a shiny metallic surface an d varied in color from golden brown (low temperature depositions) to grayish (high temp erature depositions). Films deposited from 25 and 26 had a similar appearance with colors ranging fr om gray for low temperature depositions to a dark brownish, almost purple appear ance at high temperature depositions. Film Composition AES results for films deposited from 24 between 300 and 650 C i ndicated the presence of W, N, C, and O in varying concentration (Figur e 3-2), whereas films depos ited at 700 C showed presence of only W, C, and O. Films deposit ed in the temperature range from 300 to 650 C were W rich, with W contents varying between 51 and 63 at. %. At 700 C, the W content of the film decreased to 34 at. % due to extensive incorporation of C. The N content in the film was 11 at. % for depositions at 300 C and rose to its ma ximum value of 24 at. %, for depositions at 350 C. The N content then declined with increa sing deposition temperature until it reached 5 at. % for films grown at 650 C. At 700 C, the AES m easurement showed that the film N content is below the detection limit of AES (~1 at. %). Bo th C and O were presen t in appreciable amounts in the deposited films. The C content of the films remained unchanged at ca. 9 at. % for depositions between 300 and 400 C. Above 400 C, the general trend was for the carbon content to increase with increas ing deposition temperature, with a rapid increase for films grown above 650 C, most likely due to increased inco rporation of C from the precursor and/or benzonitrile into the film.122 The O content of the film decr eased from 19 to 2 at. % over the range of growth temperature, with lower values for depositions at higher temperatures. Possible sources of oxygen detected in the films include residual gas (O2 and water vapor) in the reactor incorporated during growth and expos ure to the atmosphere post-growth. 60

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0 10 20 30 40 50 60 70 80 90 100 200300400500600700800Concentration (at. %)Deposition Temperature (C) W N C OFigure 3-2. Composition of films deposited from 24 on Si (100) substrate at different deposition temperatures determined by AES after 0.5 min of sputtering. XPS results for the chemical com position of films deposited from 25 in the temperature range from 300 to 700 C showed similar results (Figure 3-3). The tungsten level was highest for films deposited at 450 C and 500 C, while the nitrogen, carbon, and oxygen concentrations were fairly steady in this range. For films deposited between 300 C to 400 C, the carbon level was below 10 at. % with the lowest value of 6 at% for depositions at 400 C. Between 500 C and 700 C, the C level increased gradually from 15 at. % to 67 at. %, an observation consistent with increased C incorporation from the alkyl substituents and the benzonitrile solvent at high temperature depositions. As the deposition te mperature increased from 300 C to 400 C, N incorporation increased from 10 at. % to 18 at. %. Above 500 C, however, the N concentration started to decrease, due to increased C incorpor ation, reaching its lowest value of 5 at. % for films deposited at 700 C. Films deposited at 300 C showed the highest level of oxygen incorporation (30 at. %) which decreased dras tically to 14 at. % at upon raising the deposition temperature to 450 C. Upon further elevation of the deposition temperature from 450 C to 700 61

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C, the oxygen level decreased gradually to eventu ally reach the lowest value of 5 at. % for deposition at 700 C. 0 10 20 30 40 50 60 70 80 90 100 200300400500600700800Concentration (at. %)Deposition Temperature (C) W N C OFigure 3-3. Composition of films deposited from 25 on Si (100) substrate at different deposition temperatures determined by XPS after 10 min of sputtering. Again, XPS measurements were performed to determine the composition of films deposited from 26 in the temperature range from 300 to 700 C (Figure 3-4). Data indicated that W, N, C, and O are present in films in varying co ncentrations over the entire temperature range. The W concentration increased steadily from 41 at. % for films deposited at 300 C to its maximum value of 56 at. % for depositions at 500 C and subsequently declined with increasing deposition temperature. The lo west C incorporation of 20 at. % was observed at a deposition temperature of 500 C. The C content gradually increased to its maximum value of 62 at. % for films deposited at 700 C which could be explai ned by increasing C incorporation from solvent decomposition and from the phenyl rings of th e precursor molecules. Furthermore, the increasing C concentration for film depositions be low 500 C may be an indicator of incomplete removal of the aromatic substituents of the pr ecursor since no such behavior was observed in 24 and 25 which solely contain aliphatic substituents. Nitrogen contents showed a slight increase 62

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from 13 to 14 at. % when the deposition temper ature was raised from 300 to 350 C. Upon further increase of deposition temperature, the N content decreased con tinuously to reach its lowest value of 4 at. % for films deposited at 700 C. The O content of films deposited from 300 to 400 C stayed fairly constant at 17 at. % and subsequently declin ed to its lowest value of 6 at. % as the deposition temperature was raised to 700 C. 0 10 20 30 40 50 60 70 80 90 100 200300400500600700800Concentration (at. %)Deposition Temperature (C) W N C OFigure 3-4. Composition of films deposited from 26 on Si (100) substrate at different deposition temperatures determined by XPS after 10 min of sputtering. Due to the presence of chloride ligands in precursors 24 26, the possibility of chlorine incorporation into the films was of interest, however, no Cl was detected in films over the entire temperature range of deposition within the det ection limits of XPS (~1 at. %). This finding indicates that removal of chlorine must be a very efficient process. Since compounds 24 26 are closely related to their tungsten imido counterparts 8 11, it can be assumed that similar mechanisms for removal of Cl, such as -bond metathesis involving H2 carrier gas or HCl elimination involving surface bound H-atoms, are res ponsible for the low Cl concentrations in the deposited films.56 63

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X-Ray Diffraction The XRD patterns for films deposited from compounds 24 26 between 300 and 500 C (250 C for 25) exhibited no peaks attributable to the films, but only peaks associated with the substrate (Si (200) K, Si (400) K, and Si (400) K reflections at 33.10, 61.75, and 69.20 2 respectively123) (Figures 3-5 3-7, respectively). The absence of other peak s in these patterns suggests that films deposited at 450 C and belo w were X-ray amorphous, with the exception of films deposited from 24 which showed onset of crystallin ity at 500 C. The XRD patterns for the films deposited between 500 and 700 C showed ev idence of crystallinity in the form of two broad peaks that lie between the standard peak positions of -W2N (37.74 2 for the (111) reflection and 43.85 2 for the (200) reflection124) and -W2C (36.98 2 for the (111) reflection and 42.89 2 for the (200) reflection125), indicating the presence of either the solid solution WNxCy or a physical mixture of -W2N and -W2C. Additional peaks at 62.58 and 74.98 2 are attributable to the (220) and (311) orientations of -WNxCy, respectively. As the deposition temperature increased to 600 C, further sharpening of the (111) and (200) -WNxCy peaks could be observed in all spectra, wh ich is indicative of a higher degree of crystallization. However, the peaks for films deposited from 25 and 26 seemed to flatten again at even higher deposition temperatures (>650 C), which may be an indicator of excess amorphous C hindering crystallization of the films. For film deposition from 24 at 700 C, the two peaks at 37.20 and 42.55 2 correspond to the -W2C phase since the films contain no detectable N as indicated by AES measurements. Furthermore, all films displayed a peak at 65.99 2 indicative of W L radiation that originates from W deposition on the target as a result of filament evaporation.126 64

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30 40 50 60 70 80Intensity (a.u.)2 (Degrees)700 C 600 C 550 C 500 C 450 C 400 C 350 C 300 CSi (200) WNxCy (111) WNxCy(200) Si (400) K Si (400) K WNxCy (311) WNxCy (220) Figure 3-5. X-ray diffraction patte rns for films deposited from 24 between 300 and 700 C on Si (100) substrate. Figure 3-6. X-ray diffraction patte rns for films deposited from 25 between 250 and 700 C on Si (100) substrate. 65 30 40 50 60 70 80Intensity (a.u.)2 (Degrees)600 C 550 C 500 C 450 C 400 C 350 C 300 C 250 C 650 C 700 CSi (200) WNxCy (111) WNxCy(200) Si (400) K Si (400) K WNxCy (311) WNxCy (220)

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Figure 3-7. X-ray diffraction patte rns for films deposited from 26 between 300 and 700 C on Si (100) substrate. The ability to deposit amorphous films from precursors 24 26 at temperatures at and below 450 C is highly significant for diffusion ba rrier applications si nce the formation of polycrystalline barriers can f acilitate diffusion of Cu to th e underlying Si via the grain boundaries. Growth Rates The growth rate for films deposited from 24 was determined by measuring the film thickness using X-SEM (Figure 3-8) and dividing by deposition time. The growth rate increased from 1 /min at 300 C to 13 /min for deposit ion at 450 C, then leveled off, decreasing slightly until the growth temper ature reached 650 C. For depositi on at 700 C, the growth rate increased significantly to 38 /min suggesting a change in growth mechanism at this temperature. Thus, film depositi ons at 700 C were neglected in the determination of the growth regimes since the films consisted of -W2C only, indicating a growth behavior that is not 66 30 40 50 60 70 80Intensity (a.u.)2 (Degrees)650 C 600 C 550 C 500 C 450 C 400 C 350 C 300 C 700 CSi (200) WNxCy (111) WNxCy(200) Si (400) K Si (400) K WNxCy (311) WNxCy (220)

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comparable to that of -WNxCy. Figure 3-9 depicts the Arrhenius plot for depositions from 24 (error bars indicate uncertainty due to deposition temperature variation ( C) and thickness measurement from X-SEM images). The film growth rate increased exponentially with temperature between 300 and 450 C with an a pparent activation energy of 0.52 eV, suggesting that growth is in the surface reaction limited regime. For films deposited between 450 and 650 C, the weak temperature dependence is consis tent with mass transfer limited growth. The transition from surface reaction limited to mas s transfer limited growth occurs between 450 and 500 C. Figure 3-8. SEM images for films deposited from 24 at 400 and 650 C on Si (100) substrate. Growth rates of films deposited from 25 were determined in a similar way. Figure 3-10 shows cross-sectional SEM images of the films grown at the lowest temperature (300 C) and the highest temperature (700 C), with growth rates gradually increasing from 2.7 /min at 300 C to 12.7 /min for films deposited at 500 C. Fo r depositions above 500 C, the growth rate first decreased to 9.7 /min (550 C), then increased again to 14.2 /min (600 C), and eventually increased significantly to 29.1 and 29.4 /min fo r depositions at 650 and 700 C, respectively, indicating a change in growth mechanism at these temperatures. Figure 3-11 shows the Arrhenius plot for film depositions from 25, which can be divided into two major regimes. The 67

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0 1 2 3 4 0.951.151.351.551.75ln(Growth Rate) (/min)1000/T (K-1)700 C600 C500 C400 C 300 C 700 C600 C500 C400 C 300 C Figure 3-9. Arrhenius plot for film depositions from 24 on Si (100) substrate. low temperature region (between 300 and 500 C ) corresponds to the kinetically controlled growth regime with an apparent Ea of 0.28 eV. The low Ea (compared to depositions from 8 11, and 24) may account for the significantly high er growth rates when compared to 24 and might also explain why 25 was the only precursor with acceptable film growth at temperatures as low as 250 C. The second growth regime (de positions above 550 C) showed uncharacteristic behavior and does not allow for identification of a well defined ma ss transfer controlled growth regime. Figure 3-10. SEM images for films deposited from 25 at 300 and 700 C on Si (100) substrate. 68

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0 1 2 3 4 0.951.151.351.551.75ln(Growth Rate) (/min)1000/T (K-1)700 C600 C500 C400 C 300 C Figure 3-11. Arrhenius plot for film depositions from 25 on Si (100) substrate. Again, the growth rates of films deposited from 26 were determined by measuring film thickness via the obtained X-SEM images followed by dividing th rough the deposition time. Figure 3-12 shows the cross-sec tional SEM images of the films grown at 400 and 600 C. The growth rates increased from 1.0 /min at 300 C to 7.0 /min at 450 C, then stayed relatively constant (~8 /min) for depositions from 500 to 550 C, and finally showed a steady increase towards 25.4 /min (700 C) for films deposited above 600 C indicating that a subtle change in Figure 3-12. SEM images for films deposited from 26 at 400 and 600 C on Si (100) substrate. 69

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mechanism might be occurring at elevated depos ition temperatures. Neve rtheless, two growth regimes were identified in the Arrhenius plot for film depositions from 26 (Figure 3-13). An apparent activation energy of 0.49 eV could be determined from the kinetically controlled growth regime in the low deposition temperature region (between 300 and 450 C). The reaction enters the mass transfer controlled growth regime when the deposition temperatures were raised above 450 C. 1 0 1 2 3 4 0.951.151.351.551.75ln(Growth Rate) (/min)1000/T (K-1)700 C600 C500 C400 C 300 C Figure 3-13. Arrhenius plot for film depositions from 26 on Si (100) substrate. Diffusion Barrier Testing To determine the effectiven ess of film deposited from 24 as a Cu diffusion barrier, WNxCy films deposited at 350 and 400 C were coated w ith 100 nm PVD Cu. Prio r to the deposition of Cu, the barrier film was exposed to atmosphere fo r approximately 1 2 hours. The Cu/barrier/Si stack was annealed in vacuum at 500 C fo r 30 min. Three-point AES depth profiling was carried out on the annealed barrier/Si stack obta ined after removing the Cu layer by etching with dilute HNO3 which was necessary to minimize the knoc k-on effect during sputtering. Figure 3-14 shows the AES depth profile of preand post-anneal Cu/WNxCy/Si stacks for WNxCy films 70

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deposited at 350 and 400 C. The thickness of th e films deposited at 350 and 400 C was 50 and 60 nm, respectively. For deposi tion at 350 C, the pre-anneal depth profile (Figure 3-14A) showed the background signal for Cu when there is no Cu diffusion. The pre-annealed stack has a sharp barrier/Si interface, whic h is similar to that observed af ter annealing. The post-anneal Figure 3-14. Preand post-anne al AES depth profile of Cu/WNxCy /Si (100) stack for WNxCy film deposited from 24. After vacuum annealing a nd prior to AES depth profiling, the Cu layer of the Cu/WNxCy/Si stack was removed by etching. (A) Barrier deposition carried out at 350 C, no anneali ng. (B) Barrier deposition carried out at 350 C, annealing at 500 C. (C) Barri er deposition carrie d out at 400 C, no annealing. (D) Barrier deposition carried out at 400 C, ann ealing at 500 C. AES depth profile (Figure 3-14B) sh owed that the Cu signal is similar to that observed in the pre-anneal depth profile indicati ng that a 50 nm barrier film depos ited at 350 C was able to 71

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prevent bulk Cu diffusion into the Si after annealing at 500 C in vacuum for 30 min. Similar results were obtained for films deposited at 400 C (Figures 3-14C and D). A similar strategy was used to ev aluate the performance of the WNxCy thin films deposited from 25 as barriers for Cu diffusion. A layer of PVD Cu (100 nm) was deposited on a WNxCy/Si stack (barrier films deposited at 400 C) and the resulting Cu/WNxCy/Si tri-stack was subsequently annealed at 500 C under N2 for 30 min. After heat treatment, XRD and AES measurements were employed to detect Cu3Si formation that would be a result of barrier failure. The XRD measurements were done on Cu/WNxCy/Si while the AES measurements were performed on WNxCy/Si after removing the Cu layer by etching with a dilute HNO3 solution. The XRD data showed no Cu3Si peaks in the region from 44 to 46 2 as shown in Figure 3-15, indicating the absence of Cu3Si. Before heat treatment, onl y the presence of Cu (111) was 304050607080Intensity (a.u.)2 (Degrees)500C As depositedSi (200) Cu (111) Cu (200) Si (400) K Si (400) K Cu (220) Cu3Si Figure 3-15. Preand post-anneal XRD measurement of Cu (100 nm)/WNxCy/Si stack for WNxCy film deposited from 25 at 400 C. observed, whereas after heat treatment three Cu peaks were evident (Cu (111), Cu (200), and Cu (220) at 43.44, 50.80, and 74.42 2 respectively127), consistent with Cu recrystallization. AES chemical compositional depth pr ofiling (Figure 3-16) showed only a negligible background 72

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signal for Cu indicating limited Cu interdiffusion which is further corroborated by the unaffected sharp WNxCy/Si interface after annealing. Thus, WNxCy thin film (60 nm) deposited from 25 at 400 C is a suitable diffusion barrier for preven tion of Cu diffusion into Si substrates. 0 50 100 150 200Intensity (a.u.)Sputter Time (min) Cu W N C O Si WNxCy(60 nm) SiFigure 3-16. Post-anneal AES depth profile of the Cu/WNxCy/Si stack for WNxCy film deposited from 25. After vacuum anneali ng and prior to AES depth profiling, the Cu layer of the Cu/WNxCy/Si stack was removed by etching. Barrier deposition carried out at 400 C, annealing at 500 C. WNxCy thin films deposited from 26 were also subjected to di ffusion barrier testing. The diffusion barrier layer was deposited on Si substrat e at 400 C at a thickness of ~20 nm, followed by deposition of 100 nm P VD Cu on top of the WNxCy layer. The Cu/WNxCy/Si stack was subsequently annealed for 30 min at 500 C under N2. TEM images were obtained from the tristack cross-section in order to evaluate the appe arance of the materials in terfaces after the heat treatment. Additionally, EDS measurements we re performed to allow determination of the chemical composition throughout the tri-stack. TEM images (Figure 3-17A) reveal ed the interfaces between Cu/WNxCy and WNxCy/Si as fairly sharp lines, indicating limited intermixing of the materials even after the annealing process. The EDS spectrum (Figure 3-17B) showed a similar result for the Cu/WNxCy interface, 73

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with the Cu concentration dropping rapidly into the baseline throughout the barrier layer. However, EDS data for the WNxCy/Si interface showed a higher de gree of intermixing between the layers as evidenced by a significant Si concentration throughout the barrier layer and even into the Cu layer. Figure 3-17. Evaluation of barrier performance of films deposited from 26. (A) TEM image of Cu/WNxCy/Si stack with EDS profile after annealing under N2 at 500 C for 30 min. WNxCy film (~20 nm) was deposited at 400 C (B) Relative concentrations of tungsten (blue), copper (green), and silicon (red) shown in EDS profile. Conclusions It has been demonstrated that the tungsten hydrazido complexes 24 26 can be used to deposit WNxCy thin films under a H2 atmosphere in an aerosol-assisted CVD system. The H2 coreactant was required for deposition of WNxCy as experiments with 24 in an inert atmosphere (N2 carrier gas) resulted in deposition of WOx films. The lowest temperature at which film growth could be obtained was 300 C for depositions from 24 and 26, and 250 C for depositions from 25. Films deposited between 300 and 700 C (except 700 C deposition from 24) consisted of W, N, C, and O as determined by AES/XPS and no Cl impurity was detected by XPS. The highest N content (24 at. %) was de tected for films deposited from 24 and was significantly 74

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higher compared to films deposited from the analogous tungsten imido complexes 8 11 (highest value of 14 at. %), suggesting a significant contribution of the hydrazido ligand towards nitrogen incorporation. Amorphous film deposition was observed for growth below 550 C. Diffusion barrier test ing showed that WNxCy films deposited at 350 and 400 C from 24 (50 and 60 nm thick, respectively), f ilms deposited at 400 C from 25 (60 nm thick), and films deposited at 400 C from 26 (20 nm thick) were able to prevent bulk Cu diffusion after annealing at 500 C in vacuum or N2 for 30 min. Experimental Procedures Film Deposition The thin films were deposited using a custombuilt vertical quartz cold wall CVD reactor system on p-type boron doped Si (100) s ubstrates with resistivity of 1 2 -cm. The solid precursors were dissolved in benzonitrile at a co ncentration of 0.0174 mol/L, corresponding to 7.39 mg/mL, 8.09 mg/mL, and 9.55 mg/mL for compounds 24 26, respectively. The solutions were subsequently filled into a gastight syri nge and pumped into a nebulizer. A quartz plate inside the nebulizer, vibrating at a frequency of 1.44 MHz, form ed a precursor/solvent aerosol which was transported via carrier gas through a h eated transfer tube to wards a heated impinging jet. The Si substrate wafers rested on a gr aphite susceptor which was heated by RF induction coils to maintain the desired substrate temperature. The growth temperature was varied from 300 to 700 C in 50 C intervals. The system was pumped by a mechani cal roughing pump and the working pressure was maintained at 350 Torr. H2 was used as a carrier gas at a flow rate of 1000 sccm. The deposition time was fixe d at 150 min for all experiments. Film Characterization Film crystallinity was examined by XRD using a Phillips APD 3720 system. Cu K radiation, generated at 40 kV and 40 mA (1.6 kW ), was used for the XRD analysis. The XRD 75

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patterns were taken between 30 and 80 2 with step size of 0.02 /step. Film composition was determined by AES or XPS using a Perkin-Elm er PHI 660 Scanning Auger Multiprobe or a Perkin-Elmer PHI 5600 ESCA system, respectiv ely. A 5 kV acceleration voltage and 50 nA beam current was used for the Auger analysis with a beam diameter of 1 m. The sample surface was cleaned by sputter etching for 30 sec using Ar+ ions. The etch ra te for the sputtering was calibrated at 100 /min using a ta ntalum oxide standard. Since no WNxCy standard was available, elemental sensitivity factors were used to determine film composition.128 XPS spectra were taken using monochromatic Mg K radiation with the X-ray source operating at 300 W (15 kV and 20 mA). The sample surface was sputter etched for 15 min using Ar+ ions to remove surface contaminants. The etch rate for the XPS system was calibrated at 10 /min using a tantalum oxide standard. The pass energy us ed for XPS multiplex measurement was 35.75 eV and the step size of scans was 0.1 eV per step.129 The film thickness was measured by X-SEM on a JEOL JSM-6400 at a working pressure of 9.63 x 10-5 Pa and a beam working distance of 39 mm. A diced piece of the sample was attached to the SEM sample holder with the Cu side facing up (conductive Cu tape was used for suppr essing charging effects on the sample during measurements). Measurements were perf ormed with a beam emission current of 12 A and an acceleration voltage of 15 kV after alignment of the beam (alignments on gun, objective lens aperture, beam stigmation, and condenser lens). The secondary ion imag e was recorded instead of the backscattered image since the topographica l (not atomic) image was desired. The sheet resistance of the deposited films was measured using an Alessi Indus tries 4-point probe. Diffusion Barrier Testing The deposited WNxCy films were transferred in air to a multi-target sputter deposition system (Kurt J. Lesker CMS-18) where 100 nm thick Cu films were deposited. The base pressure of the system was 10-6 Torr and deposition was performed at 5 mTorr with Ar as the 76

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77 sputter deposition gas. The fo rward sputtering power for the Cu target was 250 W and the film growth rate was 240 /min. Annealing of the Cu/WNxCy/Si stacks was either performed in the sputter system at a base pressure of 10-6 Torr or in the MOCVD reactor under N2 at a pressure of 1 atm. After the heat treatment, XRD and AE S/XPS sputter depth profiling were used to examine the Cu/WNxCy/Si stacks. Cross-sectional TEM imaging (JEOL 2010F High Resolution Transmission Electron Microscope) and EDS qualitative analysis (JEOL Superprobe 733 Energy Dispersive Spectrometer) were used to invest igate the diffusion barrier performance. Both instruments were operated at a working voltage of 200 kV.

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CHAPTER 4 EFFECT OF NH3 ON FILM PROPERTIES OF MOCVD WNXCY DEPOSITED FROM 25 AND 26 Introduction Before the development of single-source precursors, NH3 was used in co-reactant based thin film depositions as the primary N source. Although modern precursors limit the need for additional N sources, addition of NH3 to the carrier gas can be a useful technique in deposition experiments to manipulate the nitrogen content of the produced films. McElwee-White and coworkers have shown that addition of NH3 can significantly increase N incorporation into films deposited from the tungsten imido precursor 8.51 Simultaneously, O and C contamination could be reduced by a considerable am ount, resulting in higher quality WNxCy films. In the following paragraphs, the effects of NH3 as a co-reactant on the prope rties of films deposited from 25 and 26 are discussed. Film Deposition from 25 and 26 with NH3 2 Film depositions were carried out with an expe rimental setup identical to the one described in Chapter 3, with the only difference being the addition of NH3 co-reactant into the carrier gas at a flow rate of 30 sccm. Film characterizatio ns were carried out using a similar set of spectroscopic tools. As descri bed previously, film crystallinit y was examined by XRD and film composition was determined via XPS after cleani ng the sample surface by sputter etching. The film thickness was measured by X-SEM, whereas the sheet resistance of the deposited films was measured via 4-point probe. Furthermore, the surface morphology of the deposited films was evaluated via atomic force microscopy (AFM) measurements. Diffusi on barrier testing was again done by deposition of a 100 nm thick PVD Cu film on top of the barrier layer, followed by 2 Film depositions and characterizations performed by Dojun Kim. 78

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annealing of the Cu/WNxCy/Si stacks and subsequent TEM, EDS, and XPS depth profiling experiments. X-Ray Diffraction Films deposited from 25 and NH3 in a temperature range from 300 to 450 C resulted in deposition of X-ray amorphous films, as had been observed in depositions without NH3 (Figure 4-1). Material grown with NH3 at 500 and 550 C was also amorphous, in contrast to polycrystalline films grown without NH3 at 500 C and above. This phenomenon may be due to surface site blocking and insufficient surface diffusion of NH3 at lower deposition temperatures. Films grown at 600 C showed signs of polycryst alline growth as evidenced by the appearance of two peaks at 37.24 and 42.98 2 consistent with the (111) and (200) orientations of WNxCy, respectively. Peaks corresponding to the (220) and (311) orientations at 62.58 and 74.98 2 respectively, were not clea rly visible. Upon furthe r increase in deposition 30 40 50 60 70 80Intensity (a.u.)2 (Degrees)Si (200) WNxCy (111) WNxCy(200) Si (400) K Si (400) K WNxCy (311) 650 C 600 C 550 C 500 C 450 C 400 C 350 C 300 C 700 C WNxCy (220) Figure 4-1. X-ray diffraction patte rns for films deposited from 25 and NH3 between 300 and 700 C on Si (100) substrate. 79

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temperature to 650 C, the peaks associated with -WNxCy seemed to flatten out again until they merged into the baseline for de positions at 700 C, which is in dicative of a lower degree of polycrystalline grain growth. Films deposited from 26 in the temperature range from 300 to 700 C showed a slightly different behavior. Similar to depositions without NH3 as a co-reactant, f ilms deposited between 300 and 400 C appeared to be X-ray amorphous a nd only showed peaks attributable to the Si substrate (Figure 4-2). However, the onset of crystallinity was observed for film deposition at 450 C as evidenced by the appear ance of peaks at 37.24 and 42.98 2 corresponding to the (111) and (200) orientations of -WNxCy, respectively. The peaks sharpened with increasing deposition temperature indicating increased crystallinity of the deposited films. Contrary to depositions from 25 and NH3, the addition of NH3 as a co-reactant seemed to have an adverse effect on the microstructure of films deposited from 26. Figure 4-2. X-ray diffraction patte rns for films deposited from 26 and NH3 between 300 and 700 C on Si (100) substrate. 80 30 40 50 60 70 80Intensity (a.u.)2 (Degrees)Si (200) WNxCy (111) WNxCy(200) Si (400) K Si (400) K WNxCy (311) 650 C 600 C 550 C 500 C 450 C 400 C 350 C 300 C 700 C WNxCy (220)

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Film Composition The measured photoelectron intensities of XPS were used to identify the relative concentration of the elements present in the films deposited from 25 (Figure 4-3). Addition of NH3 as a co-reactant increased the N levels over the entire deposition temperature range. The concomitant decrease in C and O is attributed to the increased con centration of N in the films. The addition of NH3 increased the N content from 17 to 24 at. % for depositions at 400 C, resulting in films with the highest N incorpora tion over the entire temperature range. As the deposition temperature increased, N levels contin uously decreased to reach the lowest value of 12 at. % for depositions at 700 C. Addition of NH3 appeared to have little impact on the C content at deposition temperatures between 300 a nd 450 C, which may reflect a change in the reaction kinetics of carbon removal processe s between low and high temperature. At temperatures of 500 C and above, the C conten t of the films was significantly lower for depositions with NH3 than for depositions without NH3. Enhanced NH3 decomposition at increased temperatures may improve production of gaseous carbon species such as CH4, a phenomenon that can lead to C depletion in films deposited at high temperatures.51 A decrease in O levels was observed for de positions over the entire temperature range, with the most significant change fr om 33 at. % for depositions without NH3 to 22 at. % for depositions from 25 with NH3 occurring at 350 C. As the te mperature increased, O levels decreased to reach the lowest concentration of 4 at. % for depositions at 700 C. The W concentrations seemed to be mostly unaffected for depositions with NH3 between 300 and 600 C compared to depositions without NH3. Only for depositions at 650 and 700 C could a slight increase in W content be obser ved. Once again, no Cl contamina tion was detected within the detection limits of XPS, indicating that the Cl removal processes remain effective even after addition of NH3 into the carrier gas. 81

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0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)W 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)N 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)C 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)O Figure 4-3. Comparison of film composition deposited from 25 with NH3 (blue) and without NH3 (red) on Si (100) substrate at differe nt deposition temperatures determined by XPS after 10 min of sputtering. Although the effects of W, N, and C stoichio metries on diffusion barrier performance are not well understood, a thermodynamically stable barrier is desirable as it is more likely to resist temperature induced degradation or oxidation. Since -W2N is the most stable form of tungsten nitride, N/W ratios of roughly 0.5 can indicate the formation of a stable diffusion barrier. Depicted in Figure 4-4 is th e dependence of N/W ratios on deposition temperature for film depositions from 25 with and without NH3. Consistent with increased N incorporation as determined by XPS, the N/W ratios we re higher for depositions with NH3 over the entire temperature range. The highest N/ W ratio of 0.46 for deposition from 25 with NH3 was observed at a deposition temperat ure of 400 C which is in good agreement with the highest N incorporation observed for all films. 82

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 200300400500600700800N/W RatioDeposition Temperature (C) Figure 4-4. Dependence of N/W ratios on deposi tion temperature for films deposited from 25 with and without NH3. The relative atomic concentrations of films deposited from 26 and NH3 in the temperature range from 300 to 700 C were determined via XPS measurements (Figure 4-5). Similar to depositions without NH3, W, N, C, and O were observed in fi lms in varying concentrations over the entire temperature range. With the excepti on of films deposited at 300 and 350 C, addition of NH3 as a co-reactant resulted in elevated N cont ent over the entire temperature range. The highest N incorporation of 19 at % was detected for deposition at 450 C compared to 14 at. % for deposition at 350 C without NH3. The N levels remained relatively constant for depositions between 400 and 600 C and then showed a decr ease towards 11 at. % for films deposited at 700 C. The increase in N levels in the high te mperature range may account for the concurrent decrease in C content. The lowest C incorporat ion of 14 at. % was detected for depositions at 350 C, which is significantly lower than the observed 28 at. % for depositions at the same temperature in the absence of NH3. The drop in C levels may be explained by an average increase of 8 at. % in W concentration at low deposition temperatures (300 and 350 C). The W content decreased to 46 at. % at 450 C, then increased to reach its highest value of 51 at. % at 83

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550 C and subsequently decreased to its lowest value of 33 at. % for depositions at 700 C. Addition of NH3 into the carrier gas seemed to have a limited effect on the O concentration of the deposited films over the entire temperature range. The highest O level of 21 at. % was observed for depositions at 350 C followed by a continuous decrease towa rds the lowest value of 5 at. % for film depositions at 700 C. Agai n, no Cl contamination was observed within the detection limit of XPS. 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)W 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)N 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)C 0 10 20 30 40 50 60 70 80 90 100 250350450550650750Concentration (at. %)Deposition Temperature (C)O Figure 4-5. Comparison of film composition deposited from 26 with NH3 (blue) and without NH3 (red) on Si (100) substrate at differe nt deposition temperatures determined by XPS after 10 min of sputtering. Chemical Bonding States Bonding of W, N, C, and O in the films deposited from 25 and NH3 between 300 and 700 C was investigated by XPS and compared to films deposited from 25 without NH3. The major photoelectron lines were W 4f, N 1s C 1s and O 1s, which were used to investigate the chemical 84

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bonding states of the four elements present in the films. The W 4f photoelectron line is a doublet due to spin-orbit coupling affecting W 4f7/2 and W 4f5/2, whereas the N 1s, C 1s and O 1s photoelectron lines are singlets. Figure 4-6 compares the change of XPS patterns of the W 4f bindi ng energy (BE) as the deposition temperature changed for films deposited from 25 with and without NH3. The major W 4f7/2 and W 4f5/2 peaks for depositions at 400 C without NH3 were at 31.6 and 33.5 eV, respectively, and correspond well to literature values for WCx and WNx (Table 4-1). Both peaks were outside the margins for metallic W and WO3, indicating that W is bound to both C and N and was therefore mostly present as -WNxCy. At lower deposition te mperatures (300 and 350 C), a large portion of th e peak corresponded to WO3 (~36 and 37.7 eV), indicating that WO3 formation was dominant in this temperature rang e. Similar behavior was observed for film depositions from 25 and NH3. WO3 was dominant at low depos ition temperatures, whereas WNxCy became the prevailing species in the films at higher deposition temperatures. Since films 25 30 35 40 45Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C W 4f (withoutNH3) 25 30 35 40 45Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C W 4f (withNH3)Figure 4-6. Evolution of bindi ng energies (W 4f) with deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. 85

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Table 4-1. Literature values of relevant binding energies. W 4f7/2 W 4f5/2 N 1s C 1s O 1s Metallic Tungsten130-132 31.2-31.7 33.4 WNx 131-135 32.7-33.6 33.3-35.8 396.2-398.2 Nitrogen (Grain Boundary)11,35 399.2-400.0 WO3 11,131-133,136 35.5-36.7 37.6-37.8 528.2-531.6 WCx 130-132,137 31.6-32.3 33.7-33.9 279.7-283.8 Amorphous Carbon131,132,138,139 284.2-285.2 deposited with NH3 showed higher N concentrations, the transition from WO3 to WNxCy occurs at 350 C as compared to 400 C for depositions without NH3. The change of XPS patterns for N 1s BE w ith varying deposition temperatures was also compared for films deposited from 25 with or without NH3 (Figure 4-7). For depositions without NH3, the N 1s peaks were located at 397.3 eV, consistent with literature values for WNx (Table 4-1). The absence of peaks at 400.0 eV suggested that all nitrogen is bound to W in the form of WNx ruling out the possibility of nitrogen at the grain boundaries.11 As expected, the maximum nitrogen intensity was observed for depositions at 400 C, which corresponds to films with the highest nitrogen incorporation. For depositions with NH3 as a co-reactant, the nitrogen intensity was much higher over the entire temperature ra nge, an observation that is in good agreement with the elevated N levels at all deposition te mperatures. Again, a single N 1s peak at an identical peak position (397.3 eV) indicated that nitrogen can be found in similar W-N bonding states with the increased sharpness of the N 1s peak being another indicator for higher N levels in the deposited films. 86

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391 396 401Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C N 1s (withoutNH3) 391 396 401Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C N 1s (withNH3)Figure 4-7. Evolution of binding energies (N 1s) with deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. XPS patterns of the C 1s BE for films deposited from 25 with and without NH3 were investigated as well. For depositions at lo w temperatures, C 1s peaks at 283.1 eV are the predominant features of the XPS spectra (Figure 4-8). This peak position is in good agreement with the literature value of WCx, indicating that most C atoms ar e bound to W. As the deposition temperature was raised to 600 C and above, the C 1s peaks started to shift towards 284.5 eV, indicating the presence of a mixtur e of amorphous C outside the WCx lattice and W-bound carbon atoms. The ratio of amorphous carbon to WCx seemed to increase with increasing deposition temperatures, an observation that co rresponds well to the steep increase in C concentration as deposition temperatures were ra ised above 600 C. This behavior was not as predominant in depositions with NH3, as the overall C levels in the deposited films were decreased especially at high deposition temperatures The shift towards graphitic C seemed to be delayed until deposition temperatures reached 700 C, indicating that over most of the temperature range C can be found as part of the WNxCy lattice. 87

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276 278 280 282 284 286 288Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C C 1s (withoutNH3) 276 278 280 282 284 286 288Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C C 1s (withNH3)Figure 4-8. Evolution of binding energies (C 1s) with deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. The XPS patterns of the O 1s BE fo r both depositions with and without NH3 showed similarities over the entire depos ition range (Figure 4-9). The O 1s peaks at 530.3 eV, consistent with WO3 (Table 4-1), showed their highest inte nsities at low temperatures, which was consistent with the highest O incorporation. As the deposition temperatur e increased to 650 C, 524 526 528 530 532 534 536Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C O 1s (withoutNH3) 524 526 528 530 532 534 536Intensity (a.u.)Binding Energy (eV) 300 C 350 C 400 C 450 C 500 C 550 C 600 C 650 C 700 C O 1s (withNH3)Figure 4-9. Evolution of binding energies (O 1s) with deposition temperature for films deposited from 25 with and without NH3 determined by XPS after 10 min of Ar sputter. 88

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the O 1s peaks decreased in intensity due to decr easing O levels in the deposited films. Film depositions with NH3 showed lower overall O 1s intensities, consistent with lower O content of the films compared to deposition without NH3. Depositions at 700 C showed a slight shift in the O 1s peaks towards 531.8 eV indicative of O atoms bound to WNxCy.140 Growth Rates Figure 4-10 shows SEM cross-sect ional images of the films grown at 300 and 600 C. The deposition rates for films grown from 25 and NH3 ranged from 0.6 /min at low temperatures to 4.2 /min at high temperatures, which is significantly lower than the observed growth rates of 2.7 /min to 29.4 /min for film depositions without NH3. Again, surface site blocking and limited diffusivity of NH3 at low deposition temperatures may account for this observation. Figure 4-11 depicts the change in growth rates with deposition temperature for films deposited from 25 and NH3. A transition from a kinetica lly controlled growth regime (Ea = 0.39 eV) at low temperatures to a diffusion limited growth regime can be observed near 450 C. The decrease in growth rate for films grown at 650 and 700 C might be a result of a change in growth mechanism; however, no definitive information can be deduced from the plot. This nonFigure 4-10. SEM images for films deposited from 25 and NH3 at 300 and 600 C on Si (100) substrate. 89

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traditional behavior at deposition temperatures above 600 C is consistent with the irregular behavior seen in the XRD spectra of films deposited at 650 and 700 C which suggest that film growth at high temperatures is outside the margin for regular WNxCy films. Furthermore, the sharp increase in C concentration of films deposited from 25 and NH3 above 600 C might be contributing to the unexpected growth behavior. 1 0 1 2 0.951.151.351.551.75ln(Growth Rate) (/min)1000/T (K-1)700 C600 C500 C400 C 300 C 700 C600 C500 C400 C 300 C Figure 4-11. Arrhenius plot for film depositions from 25 and NH3 on Si (100) substrate. Figure 4-12. SEM images for films deposited from 26 and NH3 at 400 and 600 C on Si (100) substrate. 90

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Cross-sectional SEM images of films grown from 26 and NH3 at 400 and 600 C are shown in Figure 4-12. The observed growth ra tes show a continuous increase from 7.3 to 14.3 /min when the deposition temperature was raised from 300 to 700 C. The Arrhenius plot (Figure 4-13) shows mass transfer controlled growth behavior over the entire temperature range with an upper limit for th e activation energy of 0.08 eV. 0 1 2 3 4 0.951.151.351.551.75ln(Growth Rate) (/min)1000/T (K-1)700 C600 C500 C400 C 300 C Figure 4-13. Arrhenius plot for film depositions from 26 and NH3 on Si (100) substrate. Film Resistivity The pattern of film resistivity for film depositions from 25 with and without NH3 is shown in Figure 4-14. The lowe st resistivity of 290 -cm was observed for deposition at 300 C with increasing film resistivities at higher temperatur es, possibly caused by interplay of polycrystal grain growth, C content, N levels, and O contam ination over the entire temperature range. At lower deposition temperatures, an increase in N levels may account for the low film resistivities since WNx is more conductive than WO3. The highest film resistivity of 5,450 -cm was observed for depositions at 600 C. Compared to depositions without NH3, overall film resistivities for depositions with NH3 decreased drastically in the low temperature range (300 to 91

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450 C) due to the high N contents of the films. High conductivity is a desirable film property since resistivities of less than 400 -cm are required for barrier application.141,142 0 2000 4000 6000 8000 10000 200300400500600700800Film Resistivity ( -cm)Deposition Temperature (oC) Figure 4-14. Change of resis tivity with deposition temperature for films deposited from 25 with and without NH3. Atomic Force Microscopy To evaluate the surface morphology of the de posited films, AFM images were obtained from films deposited from 26 at 300 and 700 C (Figure 4-15A and B). To allow for determination of the effects of NH3 on the surface of the deposited films, a similar set of AFM images was obtained from films deposited from 26 and NH3 at identical temperatures (Figure 415C and D). As expected, films deposited at lo w temperatures showed a smoother surface with a surface roughness factor (Rq) of 5.0 nm for films deposited at 300 C without NH3. A highly uneven and rough surface (Rq = 87.4 nm) was detected for films deposited from 26 at 700 C without NH3. These findings are in good agreement with XRD measurements which indicated deposition of amorphous films at low temperatures compared to polycrystalline films at high deposition temperatures. Addition of NH3 as a co-reactant resulted in the formation of highly conformal layers with Rq values of 2.3 and 5.7 nm at deposition temperatures of 300 and 700 C, 92

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respectively. Not surprisingly, lower growth rates seem to have a positive effect on film conformality since filling of uno ccupied areas between growth islands is likely whereas island growth is favored at high growth rates. Figure 4-15. AFM images of films deposited from 26. (A) Deposition at 300 C without NH3. (B) Deposition at 700 C without NH3. (C) Deposition at 300 C with NH3. (D) Deposition at 700 C with NH3. Diffusion Barrier Testing To evaluate the performance of WNxCy thin films deposited from 25 and NH3, a film with a thickness of 27 nm was deposit ed on a silicon substrate via C VD at 400 C. Subsequently, 100 nm of PVD Cu were deposited on top of the barr ier layer followed by annealing at 500 C for 30 93

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min under N2. As shown in Figure 4-16, XRD data showed no Cu3Si peaks, indicating limited bulk Cu diffusion and Cu3Si formation. Only peaks at 43.44, 50.80, and 74.42 2 could be observed, corresponding to the Cu (111), (200), and (220) reflections, respectively. As shown in Figure 4-16. Preand post-anneal XRD measurement of Cu (100 nm)/WNxCy/Si stack for WNxCy film deposited from 25 at 400 C. Figure 4-17. Post-anneal AES depth profile of the Cu/WNxCy/Si stack for WNxCy film deposited from 25 and NH3. After vacuum annealing and prio r to AES depth profiling, the Cu layer of the Cu/WNxCy/Si stack was removed by etchi ng. Barrier deposition carried out at 400 C, annealing at 500 C. 304050607080Intensity (a.u.)2 (Degrees)500C As depositedSi (200) Cu (111) Cu (200) Si (400) K Si (400) K Cu (220) Cu3Si 02 04 06 08Intensity (a.u.)Sputter Time (min)0 Cu W N C O Si WNxCySi 94

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Figure 4-17, AES depth profiling experiments showed only a negligible background signal for Cu, indicating that no Cu interdiffusion had occu rred, an observation that is further corroborated by a sharp interface between WNxCy and Si. Films deposited from 26 and NH3 were also tested for thei r potential as Cu diffusion barriers. A WNxCy film (20 nm) was deposited on a Si (100) substrate wafer via CVD from 26 and NH3 at 400 C and was subsequently covered by 100 nm of PVD Cu. The TEM image (Figure 4-18A) of the Cu/WNxCy/Si stack shows sharp interfaces between each of the layers indicating limited diffusion of Si and Cu thr ough the barrier layer. Following deposition, the Cu/WNxCy/Si tri-stack was annealed under N2 for 30 min at 500 C. The post-anneal TEM image (Figure 4-18B) sh owed that the Cu/WNxCy interface was still inta ct suggesting that the barrier layer was not breached by Cu during a nnealing. This finding is corroborated by the obtained EDS spectrum (Figure 4-19) which showed a sharp drop of the Cu concentration at the Cu/WNxCy interface. Similarly, the Si levels show ed a sharp drop at the interface although data suggest that some Si diffused into the barrier layer during annealing. Figure 4-18. TEM images of the Cu/WNxCy/Si stack. (A) Barrier deposition carried out at 400 C, no annealing. (B) Barrier deposition carried out at 400 C, annealing at 500 C. 95

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00.020.040.060.080.1Intensity (a.u.)Distance ( m) Cu W SiFigure 4-19. EDS profile of the Cu/WNxCy/Si stack after annealing under N2 at 500 C for 30 min. Conclusions Compounds 25 and 26 were successfully used to deposit WNxCy thin films in the presence of NH3, allowing an investigation of the effects of NH3 on the film properties. The chemical composition of the deposited films showed an in crease in N incorporation with a simultaneous decrease in O contamination compared to films grown from 25 without NH3 as a co-reactant. Similarly, an increase in N levels of films deposited from 26 and NH3 was observed; however, the O levels were similar to depositions without NH3. XRD measurements suggest that addition of NH3 as a co-reactant had a mixed influence on th e film microstructure Films grown from 25 below 550 C were X-ray amorphous with limited crystallinity even at elevated deposition temperatures (between 600 and 700 C), whereas films grown from 26 showed onset of crystallinity at temperatures as low as 450 C. Growth rates varied from 0.6 to 4.2 /min ( 25) and from 7.3 to 14.3 /min (26) for deposition between 300 and 700 C and were typically lower than the observed growth rates for depositions without NH3. Surface morphology measurements suggest that addition of NH3 had a positive effect on film conformality for films deposited from 96

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26. Changes in film resistivity due to interp lay of N, C, and O content were observed for deposition from 25 at 300 C with the lowest observed resistivity of 290 -cm. Films deposited from 25 and 26 and NH3 at 400 C (27 and 20 nm, resp ectively) are viable diffusion barriers for prevention of Cu diffusion into Si as evidenced by TEM, EDS, XRD, and XPS depth profiling experiments. Experimental Procedures Film Deposition The thin films were deposited using a custombuilt vertical quartz cold wall CVD reactor system on p-type boron doped Si (100) s ubstrates with resistivity of 1 2 -cm. The solid precursors 25 and 26 were dissolved in benzonitrile at concentrations of 0.0174 mol/L (8.09 and 9.55 mg/mL, respectively). The solutions were s ubsequently filled into a gastight syringe and pumped into a nebulizer. A quartz plate inside the nebulizer, vibrati ng at a frequency of 1.44 MHz, formed a precursor/solvent aerosol which wa s transported via carrier gas through a heated transfer tube towards a heated impinging jet. The Si substrate wafers rested on a graphite susceptor which was heated by RF induction coils to maintain the desired substrate temperature. The growth temperature was varied from 300 to 700 C in 50 C intervals. The system was pumped by a mechanical roughing pump and the wo rking pressure was maintained at 350 Torr. H2 was used as a carrier gas at a flow rate of 1000 sccm, while NH3 was used as the co-reactant at a flow rate of 30 sccm. The deposition tim e was fixed at 150 min for all experiments. Film Characterization Film crystallinity was examined by XRD using a Phillips APD 3720 system. Cu K radiation, generated at 40 kV and 40 mA (1.6 kW ), was used for the XRD analysis. The XRD patterns were taken between 30 and 80 2 with step size of 0.02 /step. Film composition was determined by AES or XPS using a Perkin-Elm er PHI 660 Scanning Auger Multiprobe or a 97

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Perkin-Elmer PHI 5600 ESCA system, respectiv ely. A 5 kV acceleration voltage and 50 nA beam current was used for the Auger analysis with a beam diameter of 1 m. The sample surface was cleaned by sputter etching for 30 sec using Ar+ ions. The etch rate for sputtering was calibrated at 100 /min using a ta ntalum oxide standard. Since no WNxCy standard was available, elemental sensitivity factors were used to determine film composition.128 XPS spectra were taken using monochromatic Mg K radiation with the X-ray source operating at 300 W (15 kV and 20 mA). The sample surface was sputter etched for 15 min using Ar+ ions to remove surface contaminants. The etch rate for the XPS system was calibrated at 10 /min using a tantalum oxide standard. The pass energy us ed for XPS multiplex measurement was 35.75 eV and the step size of scans was 0.1 eV per step.129 The film thickness was measured by X-SEM on a JEOL JSM-6400 at a working pressure of 9.63 x 10-5 Pa and a beam working distance of 39 mm. A diced piece of the sample was attached to the SEM sample holder with the Cu side facing up (conductive Cu tape was used for suppr essing charging effects on the sample during measurements). Measurements were perf ormed with a beam emission current of 12 A and an acceleration voltage of 15 kV after alignment of the beam (alignments on gun, objective lens aperture, beam stigmation, and condenser lens). The secondary ion imag e was recorded instead of the backscattered image since the topographica l (not atomic) image was desired. The sheet resistance of the deposited films was measured using an Alessi Industries 4-point probe. The surface roughness was measured by AFM using a Veeco Dimension 3100 Scanning Probe Microscope. Measurements were performed in tapping mode at a 2 Hz scan rate with a 512 by 512 resolution. Diffusion Barrier Testing The deposited WNxCy films were transferred in air to a multi-target sputter deposition system (Kurt J. Lesker CMS-18) where 100 nm thick Cu films were deposited. The base 98

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99 pressure of the system was 10-6 Torr and deposition was performed at 5 mTorr with Ar as the sputter deposition gas. The fo rward sputtering power for the Cu target was 250 W and the film growth rate was 240 /min. Annealing of the Cu/WNxCy/Si stacks was either performed in the sputter system at a base pressure of 10-6 Torr or in the MOCVD reactor under N2 at a pressure of 1 atm. After the heat treatment, XRD and AES/ XPS sputter depth profiling were used examine the Cu/WNxCy/Si stacks. Cross-sectional TEM imaging (JEOL 2010F High Resolution Transmission Electron Microscope) and EDS qualitative analysis (JEOL Superprobe 733 Energy Dispersive Spectrometer) were used to invest igate the diffusion barrier performance. Both instruments were operated at a working voltage of 200 kV.

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CHAPTER 5 SYNTHESIS AND CHARACTERIZATI ON OF DIORGANOH YDRAZIDO(2-) GUANIDINATE/AMIDINATE TUNGSTEN COMPLEXES Guanidinate/Amidinate Complexes in MOCVD Examples of transition metals complexed by guanidinate ligands can be found in the literature as early as the 1970s when Lappert and co-workers synthesized a Zr-guanidinate complex by reacting Zr-amides with carbodiimides.143 The excellent electronic and steric versatility of the anionic guanidinate molecule, which is due to variation of C and N atoms in the ligand backbone, renders these ligan ds suitable for complexation of most transition metals as well as f-block and main group metals (Figure 5-1A).144,145 Furthermore, its use as a substitute for cyclopentadiene in catalysis applications ha s led to a series of extensive investigations.146-160 As a result, a wealth of metal guanidinate complexes has become available over the years.161-163 Amidinates, which are based on similar ligand architecture, have recently received renewed attention as single-source precurs ors for thin film depositions of predominantly late transition metal nitrides and oxides via CVD and ALD (Figure 5-1B).164-169 Figure 5-1. Generic ligand structures. (A) Guanidinates. (B) Amidinates. More recently, discovery of advantageous decomposition pathways of the guanidinate ligand during MOCVD has sparked renewed interest in guanidinate ligands. The complex bonding behavior of metal guanidinate compounds results in interesting new decomposition 100

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chemistry of single-source precursors. In situ formation of an imido moiety via ligand fragmentation (Figure 5-2, Pathway A) is of partic ular interest when depositing metal nitride thin films since a strong M-N bond may result in improve d N-incorporation into the produced films. Furthermore, the possibility of carbodiimide deinse rtion resulting in the formation of an amide moiety (Figure 5-2, Pathway B) opens up new decomposition pathways.170-173 In this chapter, the synthesis and characterization of mixed hydrazido guanidinate/amidinate complexes of tungsten will be discussed. NR'2 N N LnM R R NR'2 N N LnM R R NR'2 N N LnM R R N LnM R LnMNR'2 MOCVD PathwayA PathwayB Figure 5-2. Possible decompositi on pathways of metal guanidi nate complexes during CVD. Synthesis of Diorganohydrazido(2-) Guan idinate/Amidinate Tungsten Complexes The mixed hydrazido guanidinate/amidinate tungsten complexes 28 31 were synthesized via salt metathesis by reacting compounds 24 26 with the corresponding lithium 101

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guanidinate/amidinate salts which were generated in situ by reacting carbodiimides with either lithium amide or alkyl-lithium reagents (Figure 5-3).149,174,175 Dropwise addition of the lithium guanidinate/amidinate solution to the parent hydrazido complexes at -78 C and subsequent stirring overnight at room temperature completed the reaction. After filtration and evaporation of the reaction solu tion, the crude products were extracted with either toluene or diethyl ether depending on their solubility characteristics. Pure products were obtained by repeated crystallization of the crude material from concen trated toluene or diethyl ether solutions layered with pentane at -25 C. As obser ved for their parent derivatives 24 and 25 1H and 13C NMR spectra revealed the symmetry equivalence of th e substituents on the hydrazido functionality in compounds 28 30. Additionally, all NMR spectra di splayed inequivalence between the substituents of the chelating gua nidinate or amidinate nitrogens, leading to their assignment as the mer isomers. Figure 5-3. Synthesis of compounds 28 31. 102

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X-Ray Crystallography Study Single crystals suitable for X-ra y diffraction were obtained from 28 by layering a concentrated methylene chloride solution with an equal amount of pentane followed by cooling to -25 C. As expected, compound 28 adopts a distorted octahedral geometry as shown in the ORTEP representation of 28 (Figure 5-4). The tungsten-chlo rine bonds are on the order of 2.38 which is in the expected range for W(VI)-Cl bonds, with the exception of the slightly longer W-Cl(3) bond (2.4162(11) ), possibly due to the trans influence of the amido moiety (W(1)N(4)). Although short bond dist ances of W(1)-N(1) and N(1) -N(2) of 1.753(4) and 1.320(6) respectively, are indicative of electron delocalization th roughout the hydrazido moiety, noteworthy differences from the same functionality in the parent compound 24 can be observed. Shortening of the W-N bond combined with simultaneous elongation of the N-N bond is indicative of the more imido-like bonding situati on depicted as represen tation B in Figure 2-2. Bond angles on the order of 115 around N(2), indicat ive of distortion from a planar arrangement (sp2 hybridization) towards te trahedral geometry (sp3 hybridization) caused by the steric demand of the guanidinate ligand, may account for the lowe r degree of delocaliza tion of the N(2)-based lone pair towards N(1) due to sy mmetry constraints. The strong trans influence of the dimethylhydrazido(2-) ligand is evidenced by the elongated W(1)-N(3) bond (2.214(3) ) compared to the W(1)-N(4) bond (1.974(3) ). The C(3)-N(3), C(3)-N(4), and C(3)-N(5) bond distances of 1.313(5), 1.402(5), a nd 1.348(5) respectively, are within the range for typical C(sp2)-N(sp2) bonds (~1.36 ) indicating donation of the N( 5)-based lone pair towards C(3) and simultaneous electron delocalizati on involving N(3), N(4), and N(5).176 This finding is corroborated by the sum of 359.8 for the bond angles around C(3), consistent with sp2 hybridization which is necessary for conjugation, although the torsion angle of 54.9 between the dimethylamido group and the N-C-N core of the guanidinate ligand suggests that this interaction 103

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is somewhat limited. Selected bond lengths and angles for 28 is given in Table 5-1. Crystal data and structure refinement for 28 can be found in Table 5-2. Table 5-1. Selected bond dist ances () and angles () for 28. Bond Bond Length () Bond Bond Angle () W1-N1 1.753(4) W1-N1-N2 173.8(4) W1-N3 2.214(3) N1-N2-C1 113.9(5) W1-N4 1.974(3) N1-N2-C2 115.8(4) W1-Cl1 2.3900(10) C1-N2-C2 116.2(5) W1-Cl2 2.3745(11) N1-W1-N3 163.40(16) W1-Cl3 2.4162(11) N1-W1-N4 101.14(16) N1-N2 1.320(6) N1-W1-Cl1 93.50(12) N3-C3 1.313(5) N1-W1-Cl2 96.94(12) N3-C4 1.464(5) N1-W1-Cl3 99.67(13) N4-C3 1.402(5) N3-C3-N4 107.4(3) N4-C7 1.480(5) N3-C3-N5 129.4(4) N5-C3 1.348(5) N4-C3-N5 123.0(3) Figure 5-4. Thermal ellipsoids diag ram of the molecular structure of 28. Thermal ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity. 104

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Table 5-2. Crystal data and refinement for compound 28. 28 Empirical formula C11H26Cl3N5W Formula weight 518.57 Temperature (K) 173(2) Wavelength () 0.71073 Crystal system Triclinic Space group P-1 Unit cell dimensions a = 8.4474(9) b = 8.8154(9) c = 14.8391(15) = 93.675(2) = 101.635(2) = 117.283(2) Volume (3) 946.23(17) Z 2 Density (Mg/m3) 1.820 Absorption coefficient (mm-1) 6.526 F(000) 504 Crystal size (mm3) 0.17 x 0.09 x 0.05 Theta range for data collection () 1.42 to 27.50 Index ranges -10 h 10 -11 k 11 -17 l 19 Reflections collected 6435 Independent reflections (Rin t ) 4228 (0.0647) Completeness to = 24.60 (%) 97.5 Absorption correction Integration Max. and min. transmission 0.7362 and 0.4034 Refinement method Full-matrix L.S. on F2Data / restraints / parameters 4228 / 0 / 181 Goodness-of-fit on F2 1.031 R1a 0.0334 wR2 b 0.0876 Largest diff. peak and hole/e3 2.299 and -1.753 R1 = (||Fo| |Fc||) / |Fo| wR2 = [ [w(Fo 2 Fc 2)2] / [w(Fo 2)2]]1/2 S = [ [w(Fo 2 Fc 2)2] / (n-p)]1/2 w = 1/[ 2(Fo 2)+(m*p)2+n*p] p = [max(Fo 2,0)+ 2* Fc 2]/3 m & n are constants. 105

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Mass Spectrometry To prescreen the hydrazido/amidinate compounds for potential application as single-source precursors for MOCVD of WNxCy films, mass spectra were obtained from compounds 29 31. Table 5-3 summarizes the major fragment ions observed in the positive ion CI spectra of compounds 29 31. Unlike 24, 25, and 26, compounds 29, 30, and 31 do not contain weakly bound solvent molecules such as acetonitrile which could result in facile fragmentation. Thus, molecular ion peaks were observed in the CI spectra of 29 31 in mass envelopes at 490, 530 and 614, respectively. Loss of a methyl group resulting in fragments with m/z 475 for 29 and 515 for 30 was a common feature for compounds 29 and 30. Loss of Cl from the parent complexes 29 31 yielding fragments at m/z 453, 493 and 577, respectively, was observed in the CI spectra of all compounds. Also, complete dissociation of the amidinate ligand occured under ionization conditions as ev idenced by fragments at m/z 142 corresponding to [iPrNC(Me)NiPr]+ in all spectra. Cracking of the N-C(quaternary) bond of the am idinate ligand resulting in the formation of two fragments, [iPrNCCH3]+ and [iPrNH]+, with mass envelopes at m/z 84 and 58, respectively, was observed in the spectrum of 29. Similar fragments were identified in the CI spectra of compounds 30 and 31 indicating similar decomposition be havior. The occurrence of N-N bond cleavage from 30, resulting in the formation of the [pip]+ fragment, may be contributing to the peak at m/z 84, however, overlapping peak positions with the [iPrNCCH3]+ fragment in the mass spectra do not allow for definitive peak assignment. Similar to the parent compound 24 no N-N bond cleavage products could be id entified in the spectrum of 29. On the contrary, fragments at m/z 167, 168, 169 and 170 in the spectrum of compound 31 are indicative of the N-N bond cleavage products [Ph2N-H]+, [Ph2N]+, [Ph2NH]+, and [Ph2NH2]+, respectively, similar to the fragmentation pattern observ ed for the parent complex 26. 106

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Table 5-3. Summary of relative abundances for positive ion CI mass spectra of compounds 29 31. Compound CI Fragments m/z abundancea 29 {[iPrNC(Me)NiPr]Cl3W(NNMe2)}+ = [M]+ 490 23 [M-CH3]+ 475 12 [M-Cl]+ 453 100 [iPrNC(Me)NiPr]+ 142 22 [iPrNCCH3]+ 84 55 [iPrNH]+ 58 20 30 {[iPrNC(Me)NiPr]Cl3W(N-pip)}+ = [M]+ 530 37 [M-CH3]+ 515 10 [M-Cl]+ 493 100 [M-Cl3-CH3]+ 409 8 [iPrNC(Me)NiPr]+ 142 4 [pip]+ and/or [iPrNCCH3]+ 84 54 31 {[iPrNC(Me)NiPr]Cl3W(NNPh2)}+ = [M]+ 614 21 [M-Cl]+ 577 43 [Ph2NH2]+ 170 34 [Ph2NH]+ 169 42 [Ph2N]+ 168 68 [Ph2N-H]+ 167 44 [iPrNC(Me)NiPr]+ 142 11 [iPrNCCH3]+ 84 100 a Relative abundances were adjusted by summing the observed intensities fo r the predicted peaks of each mass envelope and normalizing the largest sum to 100%. Alternate Synthetic Pathways Modified Lithium Guanidinate Reagents Major drawbacks of the synthetic procedure described previously are the low reaction yields and the nontrivi al product purification. To overcom e some of these shortcomings, alternate synthetic pathways were explored wi th the intention of attaining acceptable product yields. Lithium amides and related compounds such as lithiated guanidinates and amidinates are known for their high reducing power towards high valent group 6 tran sition metals including tungsten. Fast electron transfer to the meta l center with subsequent decomposition of the complexes through radical initiated reactions may account for low yields as well as the inability to recover any starting materials. Stabilizing the lithium guanid inate reagents with coordinating 107

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solvents could potentially tilt the ratio of electron transfer versus metal ligation in favor of the metal complexes, thus allowing for less decomposition and higher reaction yields. Synthesis Compound 32 was prepared by employing a synthetic strategy similar to the one described previously for compounds 28 30. The lithium guanidinate reagent was generated in situ by reacting N,N -diisopropylcarbodiimide with a stoichiometric amount of lithiumbistrimethylsilylamide (Figure 5-5) followe d by addition of tetramethylethylenediamine (TMEDA). Pure 32 was obtained as a white solid by removing the solvent under reduced pressure. 1H and 13C NMR spectra are indicative of a hi ghly symmetric compound as evidenced by a single peak for each substituent of both the chelating guanidinate li gand and the coordinated TMEDA solvent molecule. Figure 5-5. Synthesis of compound 32. X-ray crystallography study Single crystals of 32 suitable for X-ray diffraction were grown from a concentrated hexane solution at -25 C. Compound 32 crystallizes in a distorted tetrahedral geometry around the central lithium atom as shown in the ORTEP representation of 32 (Figure 5-6). TMEDA is coordinated in a bidentate fashion with equal Li -N bond lengths of ~2.10 which is within the expected range for lithium(I)-nitrogen(amine) bonds.177,178 Identical bond lengths for the Li108

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N(1) and Li-N(2) bonds of 1.975(4) and 1.976(4) respectively, in comb ination with similar N(1)-C(1) and N(2)-C(1) bond leng ths of 1.325(2) and 1.320(2) respectively, are indicative of a high degree of electron delocalization within the N(1)-C(1)-N(2) unit. The relatively long C(1)-N(3) bond (1.468(2) ) suggests limited overla p of the N(3) based lone pair with the guandinate backbone. This obser vation may be explained through the steric demand of the trimethylsilyl units forcing the lone pair located on N(3) into an almost perpendicular orientation (torsion angle 88.0) with respect to the N(1)-C(1)-N (2) unit, thus complete ly restricting overlap of the electron clouds. Crystal data and structure refinement for compound 32 are shown in Table 5-5. Selected bo nd lengths and angles are shown in Table 5-4. Table 5-4. Selected bond dist ances () and angles () for 32. Bond Bond Length () Bond Bond Angle () Li1-N1 1.975(4) N1-Li1-N2 69.40(12) Li1-N2 1.976(4) N1-C1-N3 121.74(16) Li1-N4 2.097(4) N1-C1-N2 116.50(16) Li1-N5 2.103(4) N2-C1-N3 121.75(15) C1-N1 1.325(2) C1-N1-C2 123.50(16) C1-N2 1.320(2) C1-N3-Si1 116.51(12) C1-N3 1.468(2) N1-Li1-N4 130.32(18) N1-C2 1.447(2) N4-Li1-N5 86.63(14) N3-Si1 1.7387(16) Reactions of 32 with compounds 24 26 in an attempt to prepare mixed hydrazido guanidinate complexes resulted in the formation of intractable reaction mixtures from which no products could be isolated. The complete disint egration of all involved reactants leads to the assumption that decomposition reactions are occurri ng at a faster rate than metal ligation which may be a result of the high stability of 32. Amidines A particularly mild way to add ligands with amine functionalities to early transition metals proceeds through precoordination of the protonated ligand followed by in situ removal of the 109

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Table 5-5. Crystal data and refinement for compound 32. 32 Empirical formula C19H48LiN5Si2 Formula weight 409.74 Temperature (K) 173(2) Wavelength () 0.71073 Crystal system Monoclinic Space group P21/c Unit cell dimensions a = 14.5133(9) b = 10.0069(6) c = 19.1703(11) = 90 = 91.599(1) = 90 Volume (3) 3465.9(4) Z 4 Density (Mg/m3) 0.978 Absorption coefficient (mm-1) 0.139 F(000) 912 Crystal size (mm3) 0.33 x 0.19 x 0.12 Theta range for data collection () 1.40 to 27.50 Index ranges -18 h 18 -12 k 12 -24 l 13 Reflections collected 18434 Independent reflections (Rin t ) 6371 (0.0557) Completeness to = 24.60 (%) 99.8 Absorption correction Integration Max. and min. transmission 0.9835 and 0.9555 Refinement method Full-matrix L.S. on F2Data / restraints / parameters 6371 / 0 / 258 Goodness-of-fit on F2 1.034 R1a 0.0580 wR2 b 0.1469 Largest diff. peak and hole/e3 0.732 and -0.387 R1 = (||Fo| |Fc||) / |Fo| wR2 = [ [w(Fo 2 Fc 2)2] / [w(Fo 2)2]]1/2 S = [ [w(Fo 2 Fc 2)2] / (n-p)]1/2 w = 1/[ 2(Fo 2)+(m*p)2+n*p] p = [max(Fo 2,0)+ 2* Fc 2]/3 m & n are constants. 110

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Figure 5-6. Thermal ellipsoids diag ram of the molecular structure of 32. Thermal ellipsoids are drawn at 50% probability. Hydrogen atoms are omitted for clarity. proton via a base resultin g in the generation of a metal amido functionality. To investigate the viability of this synthetic route, the protonated amidine 33 was prepared according to Figure 5-7. Reaction of N,N -diisopropylcarbodiimide with methyllith ium in hexane resulted in the formation of a lithiated amidine reagent which was subsequently quenched with water to afford the protonated amidine. Pure 33 was obtained as a colorless liqui d in high yields via standard organic workup procedures followed by di stillation at atmospheric pressure. 1H and 13C NMR revealed the equivalence of the isopropyl subst ituents on both N atoms which is most likely due to fast proton exchange (on the NMR timescale) between the two nitrogens. 111

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Figure 5-7. Synthesis of compound 33. All attempts towards co mplexation of compounds 24 26 with 33 employing a variety of mild and hard bases such as triethylamine, pyr idine, and methyllithium under various conditions resulted in the formation of complexes 29 31, respectively. However, reaction yields remained unchanged (below 10%), marking no significant improvement over the previously described methods. Experimental Procedures and Syntheses General Procedures Unless specified otherwise, all manipulations were performed under an inert atmosphere (N2) using standard Schlenk or glovebox techniques All reaction solvents were purified using an MBraun MB-SP solvent purificat ion system prior to use with the exception of diethyl ether which was distilled from purple Na/benzophenone ketyl prior to use. NMR solvents were degassed by three freeze-pump-thaw cycles and stored over 4 molecular sieves in an inert atmosphere glovebox. 1H and 13C NMR spectra were recorded on Gemini 300, Mercury 300 or VXR 300 spectrometers using residu al protons of deuterated solvents for reference. Pentane (anhydrous) was used as received from Aldrich. N,N -Diisopropylcarbodiimide was degassed by three freeze-pump-thaw cycles and stored ove r 4 molecular sieves TMEDA was freshly 112

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distilled prior to use and stored over 4 molecular sieves in an inert atmosphere glovebox. All other chemicals were used as recei ved without further purification. Synthesis of [iPrNC(NMe2)NiPr]Cl3WNNMe2 (28) A Schlenk flask was charged with lith ium dimethylamide (60.0 mg, 1.18 mmol) and diethyl ether (10 mL). The resulting colorless suspension was cooled to 0 C, at which temperature N,N -diisopropylcarbodiimide (149 mg, 1.18 mmol) was added dropwise via syringe. The reaction mixture was warmed to r oom temperature over a time period of 2 h. The resulting solution of lithium guanidinate reagen t was cannula-transferred into a Schlenk flask containing a solution of 24 (500 mg, 1.18 mmol) in methylen e chloride (10 mL) at -78 C. The reaction mixture was stirred for 20 min at -78 C and was warmed to room temperature overnight. All volatiles were removed in vacuo and the remaining solid was extracted with toluene (10 mL). The solution was filtered a nd layered with pentane (10 mL) and left for crystallization at -25 C. Repeated recrystal lizations from toluene/pentane (1:1) at -25 C afforded clean 28 in 4% yield ( 22.0 mg, 0.042 mmol). 1H NMR (benzene-d6, 25 C): 4.39 (sept, 1H, C H (CH3)2), 4.14 (sept, 1H, C H (CH3)2), 3.57 (s, 6H, N(C H3)2), 2.17 (s, 6H, N(C H3)2), 1.79 (d, 6H, J = 6.4 Hz, CH(C H3)2), 1.39 (d, 6H, J = 6.4 Hz, CH(C H3)2). Synthesis of [iPrNC(Me)NiPr]Cl3W NNMe2 (29) A Schlenk flask was charged with N,N -diisopropylcarbodiimide (149 mg, 1.18 mmol) and diethyl ether (10 mL). The resulting colorless solution was cooled to -78 C, at which temperature methyllithium (0.74 mL, 1.6 M, 1.18 mm ol) was added dropwise via syringe. The reaction mixture was warmed to room temperat ure over a time period of 2 h. The resulting solution of lithium amidinate reagent was cannula-transferred into a Schlenk flask containing a solution of 24 (500 mg, 1.18 mmol) in methyl ene chloride (10 mL) at -78 C. The reaction 113

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mixture was stirred for 20 min at -78 C and was warmed to room temperature overnight. All volatiles were removed in vacuo and the remaining solid was extracted with toluene (10 mL). The solution filtered and was layered with pentane (10 mL) and left for crystallization at -25 C. Repeated recrystallizations from toluene/ pentane (1:1) at -25 C afforded clean 29 in 13% yield (75.6 mg, 0.15 mmol). 1H NMR (benzene-d6, 25 C): 3.98 (sept, 1H, C H (CH3)2), 3.80 (sept, 1H, C H (CH3)2), 3.57 (s, 6H, N(C H3)2), 1.68 (d, 6H, J = 6.5 Hz, CH(C H3)2), 1.25 (d, 6H, J = 6.5 Hz, CH(C H3)2), 0.97 (s, 3H, C H3). 13C NMR (benzene-d6, 25 C): 11.60 (N2C C H3), 22.92 (CH( C H3)2), 24.48 (CH( C H3)2), 41.28 (N( C H3)2), 52.45 ( C H(CH3)2), 53.95 ( C H(CH3)2), 172.66 (N2C CH3). Synthesis of [iPrNC(Me)NiPr]Cl3W N-pip (30) A Schlenk flask was charged with N,N -diisopropylcarbodiimide (271 mg, 2.15 mmol) and diethyl ether (20 mL). The resulting colorless solution was cooled to -78 C, at which temperature methyllithium (1.34 mL, 1.6 M, 2.15 mm ol) was added dropwise via syringe. The reaction mixture was warmed to room temperat ure over a time period of 2 h. The resulting solution of lithium amidinate reagent was cannula-transferred into a Schlenk flask containing a solution of 25 (1.00 g, 2.15 mmol) in methylen e chloride (20 mL) at -78 C. The reaction mixture was stirred for 20 min at -78 C and was warmed to room temperature overnight. All volatiles were removed in vacuo and the remaining solid was ex tracted with diethyl ether (10 mL). The obtained solution was filtered and layered with pentane (10 mL) and left for crystallization at -25 C. Repeated recrystallizat ions from diethyl ether/pentane (1:1) at -25 C afforded clean 30 in 6% yield ( 69.8 mg, 0.13 mmol). 1H NMR (benzene-d6, 25 C): 4.03 (sept, 1H, C H (CH3)2), 3.80 (t, 4H, NC H2), 3.78 (sept, 1H, C H (CH3)2), 1.68 (d, 6H, J = 6.5 Hz, CH(C H3)2), 1.46 (m, 4H, C H2), 1.32 (d, 6H, J = 6.2 Hz, CH(CH3)2), 1.05 (m, 2H, C H2), 0.95 (s, 114

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3H, C H3). 13C NMR (benzene-d6, 25 C): 11.61 (N2C C H3), 22.95 (CH( C H3)2), 23.60 ( C H2), 24.45 (CH( C H3)2), 27.12 ( C H2), 52.39 ( C H( C H3)2), 53.69 ( C H( C H3)2), 54.68 (N C H2), 172.35 (N2C CH3). Synthesis of [iPrNC(Me)NiPr]Cl3W NNPh2 (31) A Schlenk flask was charged with N,N -diisopropylcarbodiimide (230 mg, 1.82 mmol) and diethyl ether (20 mL). The resulting colorless solution was cooled to -78 C, at which temperature methyllithium (1.14 mL, 1.6 M, 1.82 mm ol) was added dropwise via syringe. The reaction mixture was warmed to room temperat ure over a time period of 2 h. The resulting solution of lithium amidinate reagent was cannula-transferred into a Schlenk flask containing a solution of 26 (1.00 g, 1.82 mmol) in methylen e chloride (30 mL) at -78 C. The reaction mixture was stirred for 4 h at -78 C and was warmed to room temperature overnight. All volatiles were removed in vacuo and the remaining solid was extracted with toluene (50 mL). The solution was filtered and the solvent removed under reduced pressure to yield crude 31 (125 mg, 0.20 mmol) in 11% yield. Clean 31 was obtained via recrystallization from a diethyl ether/pentane (1:1) mixture at -25 C. 1H NMR (benzene-d6, 25 C): 7.49-6.73 (m, 10H, Ph), 3.90 (sept, 1H, C H (CH3)2), 3.82 (sept, 1H, C H (CH3)2), 1.67 (d, 6H, J = 6.2 Hz, CH(C H3)2), 1.04 (d, 6H, J = 6.6 Hz, CH(CH3)2), 0.29 (s, 3H, C H3). Synthesis of [TMEDA]Li{iPrNC[N(SiMe3)2]NiPr} (32) A Schlenk flask was charged with lithium bistrimethylsilylamide (5.40 g, 32.3 mmol) and hexane (50 mL). One equivalent of N,N -diisopropylcarbodiimide (4.08 g, 32.3 mmol) was added via syringe and the solution was stirred for 1 h at 25 C. Subsequently, TMEDA (3.75 g, 32.3 mmol) was added to the solution via syringe. After one hour of s tirring, the solvent was removed in vacuo to yield 12.65 g of compound 32 as a white microcrystalline powder (96%, 115

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30.9 mmol). 1H NMR (benzene-d6, 25 C): 3.89 (sept, 2H, C H (CH3)2), 2.01 (s, 12H, CH2N(C H3)2), 1.80 (s, 4H, C H2N(CH3)2), 1.19 (d, 12H, J = 6.2 Hz, CH(C H3)2), 0.46 (s, 18H, Si(C H3)3). 13C NMR (benzene-d6, 25 C): 3.27 (Si( C H3)3), 28.93 (CH( C H3)2), 46.22 (CH2N( C H3)2), 46.26 ( C H(CH3)2), 56.70 ( C H2N(CH3)2), 161.33 ( C N3). Synthesis of H[iPrNC(Me)NiPr] (33) A Schlenk flask was charged with N,N -diisopropylcarbodiimide (8.06 g, 63.9 mmol) and hexane (80 mL). Methyllithium (60.0 mL, 1.6 M, 95.8 mmol) was added via syringe at 0 C and the solution was stirred for 30 min. The soluti on was then allowed to warm up to room temperature and stirred for another 3 h. Subse quently, water was added dropwise via syringe at 0 C until gas evolution ceased. The solution wa s then washed with water (2 x 100 mL) in a separation funnel followed by extrac tion of the aqueous layer with 100 mL of diethyl ether. The organic layers were combined and dried over anhydrous MgSO4. The solvent was removed under reduced pressure to yield the crude product as a pale yellow liquid. Pure 33 (7.65 g) was obtained via fractional distillation (115 C, 1 at m) as a colorless liquid (84%, 53.8 mmol). The product was identified by comparing th e NMR data to literature data for 33 .179 1H NMR (chloroform-d, 25 C): 3.65 (sept, 2H, C H (CH3)2), 1.94 (broad s, 1H, N H ), 1.73 (s, 3H, N2CCH3), 1.04 (d, 12H, J = 6.5 Hz, CH(C H3)2). Mass Spectrometry All mass spectral analyses were performed using a ThermoScientific DSQ (quadrupole MS) mass spectrometer (Thermo Finnigan, San Jose, CA) equipped with a di rect insertion probe (DIP) that was held at 50 C for 1 minute and then heated up to 280 C at 30 /min during the sample analysis. Ion source temperature wa s 150 C with methane gas at 0.5 mL/min. 116

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Crystallographic Studies X-ray data collection and structure refinement for 28 Data were collected at 173 K on a Siemens SMART PLATFORM equipped with a CCD area detector and a graphite monochromator utilizing MoK radiation ( = 0.71073 ). Cell parameters were refined using up to 8192 reflections. A full sphe re of data (1850 frames) was collected using the -scan method (0.3 frame width). The first 50 frames were re-measured at the end of data collection to monitor instrument and crystal stability (maximum correction on I was <1 %). Absorption corrections by integrat ion were applied based on measured indexed crystal faces. The structure of 28 was solved by the Direct Methods in SHELXTL6, and refined using full-matrix least squares. The non-H atoms were treated anisotropicall y, whereas the hydrogen atoms were calculated in ideal positions and were riding on their respective carbon atoms. A total of 181 parameters were refined in the final cycle of refinement using 4025 reflections with I >2 (I) to yield R1 and wR2 of 3.34% and 8.76%, respectively. The largest residual electron density peak is 2.3 e-3 and is within less than 1 from the W center thus it is probably due to its anisotropy. Refinement was done using F2. A complete list of bond lengths, bond angles, atomic coordinates of non-H atoms and thermal parameters of 28 can be found in Tables A-13 A-15 of the Appendix. X-ray data collection and structure refinement for 32 Data were collected at 173 K on a Siemens SMART PLATFORM equipped with a CCD area detector and a graphite monochromator utilizing MoK radiation ( = 0.71073 ). Cell parameters were refined using up to 8192 reflections. A full sphe re of data (1850 frames) was collected using the -scan method (0.3 frame width). The first 50 frames were re-measured at 117

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118 the end of data collection to monitor instrument and crystal stability (maximum correction on I was <1 %). Absorption corrections by integrat ion were applied based on measured indexed crystal faces. The structure of 31 was solved by the Direct Methods in SHELXTL6, and refined using full-matrix least squares. The non-H atoms were treated anisotropicall y, whereas the hydrogen atoms were calculated in ideal positions and were riding on their respective carbon atoms. A total of 258 parameters were refined in the final cycle of refinement using 4691 reflections with I >2 (I) to yield R1 and wR2 of 5.80% and 14.69%, respectively. Refinement was done using F2. A complete list of bond lengths, bond angles, at omic coordinates of non-H atoms and thermal parameters of 31 can be found in Tables A-16 A-18 of the Appendix.

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APPENDIX A TABLES OF CRYSTALLOGRAPHIC DATA Crystallographic Data for (CH3CN)Cl4WNNMe2 (24) Table A-1. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (2x 103) for 24. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) W1 0 3591(1) 2500 25(1) Cl1 1831(2) 3792(1) 1055(2) 39(1) Cl2 2001(2) 3740(1) 4466(2) 39(1) N1 0 2311(4) 2500 24(1) N2 0 1391(4) 2500 31(2) N3 0 5199(5) 2500 31(1) C1 810(10) 886(5) 1561(9) 54(2) C2 0 6033(6) 2500 31(2) C3 0 7082(5) 2500 47(2) 119

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Table A-2. Bond lengths [] and angles [] for 24 W1-N1 1.769(5) W1-N3 2.224(7) W1-Cl1 2.3374(16) W1-Cl1#1 2.3374(16) W1-Cl2 2.3562(16) W1-Cl2#1 2.3562(16) N1-N2 1.271(8) N2-C1 1.438(7) N2-C1#1 1.438(7) N3-C2 1.151(11) C1-H1A 0.98 C1-H1B 0.98 C1-H1C 0.98 C2-C3 1.451(11) C3-H3A 0.98 C3-H3B 0.98 C3-H3C 0.98 N1-W1-N3 180.000(1) N1-W1-Cl1 96.85(4) N3-W1-Cl1 83.15(4) N1-W1-Cl1#1 96.85(4) N3-W1-Cl1#1 83.15(4) Cl1-W1-Cl1#1 166.29(7) N1-W1-Cl2 95.02(3) N3-W1-Cl2 84.98(3) Cl1-W1-Cl2 89.25(7) Cl1#1-W1-Cl2 89.55(7) N1-W1-Cl2#1 95.02(3) N3-W1-Cl2#1 84.98(3) Cl1-W1-Cl2#1 89.55(7) Cl1#1-W1-Cl2#1 89.25(7) Cl2-W1-Cl2#1 169.95(7) N2-N1-W1 180 N1-N2-C1 119.1(4) N1-N2-C1#1 119.1(4) C1-N2-C1#1 121.9(7) C2-N3-W1 180.000(1) N2-C1-H1A 109.5 N2-C1-H1B 109.5 H1A-C1-H1B 109.5 120

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Table A-2. continued. N2-C1-H1C 109.5 H1A-C1-H1C 109.5 H1B-C1-H1C 109.5 N3-C2-C3 180.000(2) C2-C3-H3A 109.5 C2-C3-H3B 109.5 H3A-C3-H3B 109.5 C2-C3-H3C 109.5 H3A-C3-H3C 109.5 H3B-C3-H3C 109.5 Symmetry transformations used to gene rate equivalent atoms: #1 -x,y,-z+1/2 121

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Table A-3. Anisotropic di splacement parameters (2x 103) for 24. The anisotropic displacement factor exponent takes the form: -2 2[ h2 a*2U11 + ... + 2 h k a* b* U12 ] U11 U22 U33 U23 U13 U12 W1 28(1) 19(1) 28(1) 0 4(1) 0 Cl1 43(1) 35(1) 44(1) 5(1) 19(1) 3(1) Cl2 41(1) 30(1) 38(1) 2(1) -9(1) -1(1) N1 30(3) 15(2) 27(3) 0 6(3) 0 N2 42(4) 21(3) 30(4) 0 11(3) 0 N3 31(3) 31(3) 30(3) 0 5(3) 0 C1 57(4) 41(4) 68(5) -16(3) 17(4) 10(3) C2 37(4) 20(4) 33(4) 0 1(3) 0 C3 64(6) 18(4) 52(6) 0 -3(5) 0 122

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Crystallographic Data for (CH3CN)Cl4WN-pip (25) Table A-4. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (2x 103) for 25. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) W1 2053(1) 1776(1) 226(1) 24(1) Cl1 3583(1) 2786(1) -780(1) 44(1) Cl2 205(1) 2710(1) -386(1) 42(1) Cl3 608(1) 857(1) 1494(1) 38(1) Cl4 3965(1) 1083(1) 1336(1) 36(1) N1 1947(2) 1101(2) -1241(3) 25(1) N2 1889(3) 654(2) -2342(3) 34(1) N3 2184(3) 2676(2) 2059(3) 36(1) C1 2853(3) -81(2) -2552(3) 32(1) C2 3654(4) 97(3) -3798(4) 38(1) C3 2698(4) 319(3) -5035(4) 46(1) C4 1769(3) 1107(3) -4736(4) 38(1) C5 947(3) 930(3) -3489(3) 39(1) C6 2187(4) 3128(2) 2991(4) 35(1) C7 2163(4) 3702(3) 4198(4) 48(1) 123

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Table A-5. Bond lengths [] and angles [] for 25 W1-N1 1.752(3) W1-N3 2.237(3) W1-Cl2 2.3252(8) W1-Cl4 2.3444(8) W1-Cl3 2.3563(9) W1-Cl1 2.3609(9) N1-N2 1.265(4) N2-C1 1.461(4) N2-C5 1.473(4) N3-C6 1.134(5) C1-C2 1.503(5) C1-H1A 0.99 C1-H1B 0.99 C2-C3 1.527(5) C2-H2A 0.99 C2-H2B 0.99 C3-C4 1.516(6) C3-H3A 0.99 C3-H3B 0.99 C4-C5 1.514(5) C4-H4A 0.99 C4-H4B 0.99 C5-H5A 0.99 C5-H5B 0.99 C6-C7 1.459(5) C7-H7A 0.98 C7-H7B 0.98 C7-H7C 0.98 N1-W1-N3 178.24(11) N1-W1-Cl2 96.70(8) N3-W1-Cl2 82.11(7) N1-W1-Cl4 98.17(8) N3-W1-Cl4 83.00(7) Cl2-W1-Cl4 165.11(3) N1-W1-Cl3 95.00(9) N3-W1-Cl3 86.33(8) Cl2-W1-Cl3 90.58(3) Cl4-W1-Cl3 88.80(3) N1-W1-Cl1 92.03(9) N3-W1-Cl1 86.68(8) 124

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Table A-5. continued. Cl2-W1-Cl1 90.33(3) Cl4-W1-Cl1 88.48(3) Cl3-W1-Cl1 172.76(3) N2-N1-W1 176.6(3) N1-N2-C1 120.7(2) N1-N2-C5 120.3(3) C1-N2-C5 118.7(3) C6-N3-W1 176.9(3) N2-C1-C2 110.1(3) N2-C1-H1A 109.6 C2-C1-H1A 109.6 N2-C1-H1B 109.6 C2-C1-H1B 109.6 H1A-C1-H1B 108.2 C1-C2-C3 111.3(3) C1-C2-H2A 109.4 C3-C2-H2A 109.4 C1-C2-H2B 109.4 C3-C2-H2B 109.4 H2A-C2-H2B 108 C4-C3-C2 111.0(3) C4-C3-H3A 109.4 C2-C3-H3A 109.4 C4-C3-H3B 109.4 C2-C3-H3B 109.4 H3A-C3-H3B 108 C5-C4-C3 111.4(3) C5-C4-H4A 109.4 C3-C4-H4A 109.4 C5-C4-H4B 109.4 C3-C4-H4B 109.4 H4A-C4-H4B 108 N2-C5-C4 109.3(2) N2-C5-H5A 109.8 C4-C5-H5A 109.8 N2-C5-H5B 109.8 C4-C5-H5B 109.8 H5A-C5-H5B 108.3 N3-C6-C7 178.8(4) C6-C7-H7A 109.5 125

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Table A-5. continued. C6-C7-H7B 109.5 H7A-C7-H7B 109.5 C6-C7-H7C 109.5 H7A-C7-H7C 109.5 H7B-C7-H7C 109.5 126

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Table A-6. Anisotropic di splacement parameters (2x 103) for 25. The anisotropic displacement factor exponent takes the form: -2 2[ h2 a*2U11 + ... + 2 h k a* b* U12 ] U11 U22 U33 U23 U13 U12 W1 24(1) 24(1) 22(1) -1(1) -2(1) 0(1) Cl1 41(1) 39(1) 52(1) 11(1) 3(1) -12(1) Cl2 35(1) 39(1) 50(1) 0(1) -9(1) 10(1) Cl3 41(1) 43(1) 30(1) 0(1) 9(1) -8(1) Cl4 33(1) 41(1) 34(1) 1(1) -8(1) 8(1) N1 24(1) 29(1) 21(1) -2(1) 2(1) 2(1) N2 33(1) 48(2) 21(1) -7(1) -5(1) 12(1) N3 36(1) 34(2) 37(2) -8(1) -5(1) 1(1) C1 38(2) 31(2) 26(2) 1(1) 1(1) 9(1) C2 35(2) 47(2) 33(2) 7(2) 9(2) 13(2) C3 46(2) 66(3) 27(2) 2(2) 9(2) 14(2) C4 33(2) 50(2) 30(2) 9(2) -3(1) 7(2) C5 26(2) 67(3) 22(2) -2(2) -5(1) 12(2) C6 36(2) 32(2) 38(2) -5(1) -3(2) 3(1) C7 59(2) 42(2) 44(2) -18(2) -3(2) 6(2) 127

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Crystallographic Data for (CH3CN)Cl4WNNPh2 (26) Table A-7. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (2x 103) for 26. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) W1 8619(1) 3670(1) 3931(1) 21(1) W2 11470(1) 3834(1) 1208(1) 22(1) Cl1 9639(1) 2677(1) 3484(1) 29(1) Cl2 9695(1) 3423(1) 5148(1) 36(1) Cl3 8059(1) 4839(1) 4362(1) 38(1) Cl4 7861(1) 4079(1) 2700(1) 34(1) Cl5 10439(1) 4046(1) -14(1) 33(1) Cl6 10404(1) 4815(1) 1641(1) 30(1) Cl7 12204(1) 3457(1) 2459(1) 35(1) Cl8 12105(1) 2662(1) 821(1) 37(1) N1 7220(3) 3198(2) 3958(2) 24(1) N2 6154(3) 2829(2) 3851(2) 23(1) N3 10321(4) 4301(2) 3793(2) 28(1) N4 12846(4) 4324(2) 1191(2) 30(1) N5 13909(4) 4692(2) 1296(2) 38(1) N6 9745(4) 3203(2) 1335(2) 28(1) C1 6029(4) 2256(2) 3280(2) 22(1) C2 5151(4) 2344(3) 2630(2) 30(1) C3 5031(5) 1801(3) 2081(3) 35(1) C4 5821(5) 1191(3) 2182(3) 37(1) C5 6694(5) 1101(2) 2818(3) 34(1) C6 6808(4) 1639(2) 3395(2) 28(1) C7 5139(4) 3071(2) 4192(2) 23(1) C8 4102(4) 2618(2) 4160(2) 27(1) C9 3115(4) 2853(3) 4478(2) 31(1) C10 3180(4) 3532(3) 4848(2) 33(1) C11 4232(5) 3976(3) 4884(3) 36(1) C12 5223(4) 3754(2) 4559(3) 30(1) C13 11142(5) 4662(2) 3694(2) 29(1) C14 12182(5) 5128(3) 3568(3) 42(1) C15 14025(5) 5279(2) 1869(2) 30(1) C16 14974(5) 5181(3) 2482(3) 40(1) C17 15098(5) 5720(3) 3040(3) 53(2) C18 14281(6) 6320(3) 2976(3) 58(2) C19 13352(6) 6377(3) 2345(4) 54(2) C20 13210(5) 5858(3) 1789(3) 40(1) 128

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Table A-7. continued. C21 14937(5) 4455(3) 939(3) 35(1) C22 15923(5) 4952(3) 932(3) 38(1) C23 16929(5) 4713(3) 588(3) 40(1) C24 16881(5) 4050(3) 259(3) 47(1) C25 15842(6) 3570(3) 240(3) 50(2) C26 14898(5) 3759(3) 588(3) 43(1) C27 8893(5) 2885(2) 1444(2) 29(1) C28 7818(5) 2464(3) 1588(3) 37(1) 129

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Table A-8. Bond lengths [] and angles [] for 26 W1-N1 1.742(4) W1-N3 2.216(4) W1-Cl1 2.3191(11) W1-Cl2 2.3445(11) W1-Cl3 2.3519(11) W1-Cl4 2.3537(11) W2-N4 1.734(4) W2-N6 2.231(4) W2-Cl6 2.3195(11) W2-Cl5 2.3255(11) W2-Cl8 2.3555(11) W2-Cl7 2.3660(11) N1-N2 1.312(5) N2-C7 1.429(6) N2-C1 1.447(5) N3-C13 1.141(6) N4-N5 1.307(5) N5-C21 1.457(6) N5-C15 1.469(5) N6-C27 1.133(6) C1-C2 1.380(6) C1-C6 1.380(6) C2-C3 1.383(6) C2-H2A 0.95 C3-C4 1.376(7) C3-H3A 0.95 C4-C5 1.359(6) C4-H4A 0.95 C5-C6 1.413(6) C5-H5A 0.95 C6-H6A 0.95 C7-C8 1.376(6) C7-C12 1.388(6) C8-C9 1.376(6) C8-H8A 0.95 C9-C10 1.385(6) C9-H9A 0.95 C10-C11 1.380(7) C10-H10A 0.95 C11-C12 1.381(7) 130

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Table A-8. continued. C11-H11A 0.95 C12-H12A 0.95 C13-C14 1.453(7) C14-H14A 0.98 C14-H14B 0.98 C14-H14C 0.98 C15-C20 1.349(7) C15-C16 1.379(6) C16-C17 1.389(7) C16-H16A 0.95 C17-C18 1.380(8) C17-H17A 0.95 C18-C19 1.381(8) C18-H18A 0.95 C19-C20 1.362(7) C19-H19A 0.95 C20-H20A 0.95 C21-C22 1.392(7) C21-C26 1.395(6) C22-C23 1.422(7) C22-H22A 0.95 C23-C24 1.326(7) C23-H23A 0.95 C24-C25 1.410(8) C24-H24A 0.95 C25-C26 1.345(8) C25-H25A 0.95 C26-H26A 0.95 C27-C28 1.452(7) C28-H28A 0.98 C28-H28B 0.98 C28-H28C 0.98 N1-W1-N3 174.91(14) N1-W1-Cl1 96.58(11) N3-W1-Cl1 83.54(10) N1-W1-Cl2 99.15(11) N3-W1-Cl2 85.93(9) Cl1-W1-Cl2 90.27(4) N1-W1-Cl3 98.02(11) N3-W1-Cl3 81.87(10) 131

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Table A-8. continued. Cl1-W1-Cl3 165.39(4) Cl2-W1-Cl3 87.92(4) N1-W1-Cl4 91.80(11) N3-W1-Cl4 83.11(10) Cl1-W1-Cl4 90.29(4) Cl2-W1-Cl4 168.90(4) Cl3-W1-Cl4 88.74(4) N4-W2-N6 175.21(15) N4-W2-Cl6 96.32(13) N6-W2-Cl6 82.32(10) N4-W2-Cl5 99.02(12) N6-W2-Cl5 85.62(10) Cl6-W2-Cl5 91.38(4) N4-W2-Cl8 98.17(13) N6-W2-Cl8 83.08(10) Cl6-W2-Cl8 165.37(4) Cl5-W2-Cl8 88.38(4) N4-W2-Cl7 91.71(12) N6-W2-Cl7 83.69(10) Cl6-W2-Cl7 89.14(4) Cl5-W2-Cl7 169.13(4) Cl8-W2-Cl7 88.38(4) N2-N1-W1 169.8(3) N1-N2-C7 120.7(3) N1-N2-C1 115.0(4) C7-N2-C1 123.6(4) C13-N3-W1 175.2(4) N5-N4-W2 170.6(3) N4-N5-C21 120.9(4) N4-N5-C15 114.7(4) C21-N5-C15 123.9(4) C27-N6-W2 175.9(4) C2-C1-C6 121.4(4) C2-C1-N2 119.5(4) C6-C1-N2 119.1(4) C1-C2-C3 119.8(4) C1-C2-H2A 120.1 C3-C2-H2A 120.1 C4-C3-C2 119.2(4) C4-C3-H3A 120.4 132

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Table A-8. continued. C2-C3-H3A 120.4 C5-C4-C3 121.4(4) C5-C4-H4A 119.3 C3-C4-H4A 119.3 C4-C5-C6 120.2(4) C4-C5-H5A 119.9 C6-C5-H5A 119.9 C1-C6-C5 117.8(4) C1-C6-H6A 121.1 C5-C6-H6A 121.1 C8-C7-C12 121.1(4) C8-C7-N2 119.5(4) C12-C7-N2 119.4(4) C9-C8-C7 119.7(4) C9-C8-H8A 120.1 C7-C8-H8A 120.1 C8-C9-C10 120.1(4) C8-C9-H9A 119.9 C10-C9-H9A 119.9 C11-C10-C9 119.5(4) C11-C10-H10A 120.2 C9-C10-H10A 120.2 C10-C11-C12 121.1(4) C10-C11-H11A 119.5 C12-C11-H11A 119.5 C11-C12-C7 118.4(4) C11-C12-H12A 120.8 C7-C12-H12A 120.8 N3-C13-C14 179.5(6) C13-C14-H14A 109.5 C13-C14-H14B 109.5 H14A-C14-H14B 109.5 C13-C14-H14C 109.5 H14A-C14-H14C 109.5 H14B-C14-H14C 109.5 C20-C15-C16 123.8(4) C20-C15-N5 120.3(4) C16-C15-N5 115.8(4) C15-C16-C17 117.3(5) C15-C16-H16A 121.3 133

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Table A-8. continued. C17-C16-H16A 121.3 C18-C17-C16 120.4(5) C18-C17-H17A 119.8 C16-C17-H17A 119.8 C17-C18-C19 118.8(5) C17-C18-H18A 120.6 C19-C18-H18A 120.6 C20-C19-C18 122.1(5) C20-C19-H19A 118.9 C18-C19-H19A 118.9 C15-C20-C19 117.5(5) C15-C20-H20A 121.2 C19-C20-H20A 121.2 C22-C21-C26 121.4(5) C22-C21-N5 118.1(4) C26-C21-N5 120.4(4) C21-C22-C23 117.8(5) C21-C22-H22A 121.1 C23-C22-H22A 121.1 C24-C23-C22 120.0(5) C24-C23-H23A 120 C22-C23-H23A 120 C23-C24-C25 121.2(5) C23-C24-H24A 119.4 C25-C24-H24A 119.4 C26-C25-C24 120.7(5) C26-C25-H25A 119.6 C24-C25-H25A 119.6 C25-C26-C21 118.7(5) C25-C26-H26A 120.6 C21-C26-H26A 120.6 N6-C27-C28 178.9(5) C27-C28-H28A 109.5 C27-C28-H28B 109.5 H28A-C28-H28B 109.5 C27-C28-H28C 109.5 H28A-C28-H28C 109.5 H28B-C28-H28C 109.5 134

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Table A-9. Anisotropic di splacement parameters (2x 103) for 26. The anisotropic displacement factor exponent takes the form: -2 2[ h2 a*2U11 + ... + 2 h k a* b* U12 ] U11 U22 U33 U23 U13 U12 W1 18(1) 23(1) 23(1) -4(1) 8(1) -2(1) W2 18(1) 26(1) 24(1) -1(1) 8(1) -1(1) Cl1 25(1) 30(1) 33(1) -4(1) 10(1) 5(1) Cl2 36(1) 51(1) 22(1) 1(1) 4(1) -12(1) Cl3 37(1) 28(1) 53(1) -15(1) 21(1) -5(1) Cl4 36(1) 33(1) 31(1) 4(1) 2(1) 5(1) Cl5 36(1) 36(1) 25(1) 0(1) 4(1) -3(1) Cl6 27(1) 32(1) 33(1) -2(1) 10(1) 5(1) Cl7 35(1) 41(1) 27(1) 3(1) 6(1) 9(1) Cl8 38(1) 33(1) 42(1) -7(1) 15(1) 7(1) N1 21(2) 23(2) 28(2) -1(1) 7(2) 0(2) N2 19(2) 26(2) 27(2) -6(2) 8(2) -4(2) N3 23(2) 32(2) 31(2) 3(2) 8(2) 0(2) N4 22(2) 39(2) 31(2) -4(2) 10(2) -7(2) N5 31(2) 49(2) 36(2) -18(2) 16(2) -16(2) N6 21(2) 31(2) 33(2) 2(2) 7(2) -3(2) C1 25(2) 22(2) 21(2) -5(2) 11(2) -6(2) C2 27(3) 34(2) 30(3) 3(2) 8(2) 3(2) C3 30(3) 50(3) 25(2) -8(2) 2(2) -4(2) C4 40(3) 38(3) 36(3) -13(2) 16(2) -14(2) C5 36(3) 24(2) 44(3) 0(2) 16(2) 5(2) C6 29(3) 26(2) 30(2) 2(2) 6(2) -1(2) C7 22(2) 28(2) 20(2) 2(2) 7(2) 3(2) C8 23(2) 29(2) 28(2) 3(2) 5(2) 1(2) C9 22(3) 38(3) 34(3) 13(2) 10(2) 0(2) C10 26(3) 48(3) 30(3) 6(2) 16(2) 8(2) C11 42(3) 32(3) 37(3) -9(2) 17(2) 2(2) C12 28(3) 28(2) 34(3) -3(2) 10(2) -2(2) C13 27(3) 35(2) 27(2) 4(2) 5(2) 4(2) C14 37(3) 51(3) 38(3) 5(2) 10(2) -16(3) C15 30(3) 34(2) 29(2) -8(2) 13(2) -15(2) C16 34(3) 48(3) 41(3) 2(2) 17(3) 9(2) C17 33(3) 89(4) 34(3) -14(3) 2(3) -15(3) C18 58(4) 61(4) 67(4) -41(3) 45(3) -36(3) C19 49(4) 28(3) 95(5) 5(3) 39(4) 0(3) C20 43(3) 40(3) 42(3) 4(2) 18(3) 5(2) C21 26(3) 43(3) 36(3) 0(2) 9(2) -2(2) C22 33(3) 46(3) 37(3) 3(2) 9(2) -4(2) 135

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Table A-9. continued. C23 20(3) 58(3) 41(3) -1(2) 4(2) -7(2) C24 32(3) 62(4) 53(3) 8(3) 20(3) 10(3) C25 62(4) 39(3) 54(4) -4(3) 25(3) 2(3) C26 32(3) 31(3) 67(4) -1(2) 15(3) 1(2) C27 29(3) 32(2) 26(2) -1(2) 6(2) 0(2) C28 36(3) 42(3) 36(3) -4(2) 14(2) -10(2) 136

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Crystallographic Data for (py)Cl4WNNPh2 (27) Table A-10. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (2x 103) for 27. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) W1 3077(1) 3574(1) 720(1) 21(1) Cl1 4575(2) 1918(1) 350(1) 28(1) Cl2 2697(2) 1899(1) 1450(1) 29(1) Cl3 1223(2) 4978(1) 1023(1) 30(1) Cl4 3003(2) 5006(1) -121(1) 27(1) N1 4558(5) 4408(4) 1179(2) 25(1) N2 5726(5) 4944(4) 1529(2) 23(1) N3 1136(5) 2445(4) 108(2) 24(1) C1 6751(6) 3958(5) 1877(2) 21(1) C2 6335(7) 3293(5) 2371(2) 32(1) C3 7343(7) 2344(6) 2700(3) 39(2) C4 8700(7) 2079(6) 2534(2) 33(1) C5 9067(7) 2758(6) 2035(2) 35(1) C6 8107(7) 3692(5) 1704(2) 31(1) C7 5959(6) 6423(5) 1543(2) 23(1) C8 5083(6) 7286(5) 1126(2) 26(1) C9 5312(7) 8735(5) 1155(2) 30(1) C10 6380(7) 9317(5) 1588(2) 33(1) C11 7256(7) 8450(5) 2004(3) 33(1) C12 7056(6) 6998(5) 1984(2) 26(1) C13 1245(7) 2069(5) -466(2) 27(1) C14 110(7) 1450(5) -849(3) 35(1) C15 -1203(7) 1189(5) -666(3) 36(2) C16 -1337(7) 1571(5) -78(3) 33(1) C17 -129(7) 2190(5) 291(3) 30(1) 137

PAGE 138

Table A-11. Bond lengths [] and angles [] for 27. W1-N1 1.739(5) W1-N3 2.307(4) W1-Cl4 2.3224(12) W1-Cl1 2.3375(13) W1-Cl3 2.3525(13) W1-Cl2 2.3564(12) N1-N2 1.311(6) N2-C7 1.421(6) N2-C1 1.450(6) N3-C17 1.319(7) N3-C13 1.359(6) C1-C6 1.389(8) C1-C2 1.390(7) C2-C3 1.402(8) C2-H2A 0.95 C3-C4 1.383(8) C3-H3A 0.95 C4-C5 1.389(7) C4-H4A 0.95 C5-C6 1.370(8) C5-H5A 0.95 C6-H6A 0.95 C7-C8 1.385(7) C7-C12 1.390(8) C8-C9 1.392(6) C8-H8A 0.95 C9-C10 1.365(8) C9-H9A 0.95 C10-C11 1.389(8) C10-H10A 0.95 C11-C12 1.391(7) C11-H11A 0.95 C12-H12A 0.95 C13-C14 1.358(8) C13-H13A 0.95 C14-C15 1.362(9) C14-H14A 0.95 C15-C16 1.396(8) C15-H15A 0.95 C16-C17 1.388(8) 138

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Table A-11. continued. C16-H16A 0.95 C17-H17A 0.95 N1-W1-N3 179.13(17) N1-W1-Cl4 96.94(13) N3-W1-Cl4 83.07(10) N1-W1-Cl1 94.20(14) N3-W1-Cl1 84.93(11) Cl4-W1-Cl1 92.06(5) N1-W1-Cl3 95.55(14) N3-W1-Cl3 85.33(11) Cl4-W1-Cl3 89.26(5) Cl1-W1-Cl3 169.93(5) N1-W1-Cl2 95.30(14) N3-W1-Cl2 84.70(10) Cl4-W1-Cl2 167.73(5) Cl1-W1-Cl2 87.91(5) Cl3-W1-Cl2 88.69(5) N2-N1-W1 175.7(4) N1-N2-C7 120.0(4) N1-N2-C1 116.8(4) C7-N2-C1 123.2(5) C17-N3-C13 117.8(5) C17-N3-W1 121.5(4) C13-N3-W1 120.6(4) C6-C1-C2 121.9(5) C6-C1-N2 119.4(4) C2-C1-N2 118.7(5) C1-C2-C3 117.7(5) C1-C2-H2A 121.1 C3-C2-H2A 121.1 C4-C3-C2 120.8(5) C4-C3-H3A 119.6 C2-C3-H3A 119.6 C3-C4-C5 119.6(5) C3-C4-H4A 120.2 C5-C4-H4A 120.2 C6-C5-C4 121.0(5) C6-C5-H5A 119.5 C4-C5-H5A 119.5 C5-C6-C1 118.9(5) 139

PAGE 140

Table A-11. continued. C5-C6-H6A 120.5 C1-C6-H6A 120.5 C8-C7-C12 120.4(5) C8-C7-N2 120.3(5) C12-C7-N2 119.3(5) C7-C8-C9 119.3(5) C7-C8-H8A 120.3 C9-C8-H8A 120.3 C10-C9-C8 121.1(5) C10-C9-H9A 119.5 C8-C9-H9A 119.5 C9-C10-C11 119.5(5) C9-C10-H10A 120.3 C11-C10-H10A 120.3 C10-C11-C12 120.7(5) C10-C11-H11A 119.7 C12-C11-H11A 119.7 C7-C12-C11 119.1(5) C7-C12-H12A 120.5 C11-C12-H12A 120.5 C14-C13-N3 122.5(6) C14-C13-H13A 118.7 N3-C13-H13A 118.7 C13-C14-C15 120.1(6) C13-C14-H14A 119.9 C15-C14-H14A 119.9 C14-C15-C16 118.2(6) C14-C15-H15A 120.9 C16-C15-H15A 120.9 C17-C16-C15 118.7(6) C17-C16-H16A 120.7 C15-C16-H16A 120.7 N3-C17-C16 122.7(5) N3-C17-H17A 118.7 C16-C17-H17A 118.7 140

PAGE 141

Table A-12. Anisotropic displacement parameters (2x 103) for 27. The anisotropic displacement factor expo nent takes the form: -2 2[ h2 a*2U11 + ... + 2 h k a* b* U12 ] U11 U22 U33 U23 U13 U12 W1 22(1) 20(1) 19(1) 1(1) 2(1) -2(1) Cl1 31(1) 28(1) 26(1) 4(1) 6(1) 6(1) Cl2 37(1) 29(1) 22(1) 4(1) 7(1) -5(1) Cl3 28(1) 28(1) 35(1) -8(1) 7(1) 1(1) Cl4 30(1) 26(1) 23(1) 7(1) 1(1) -1(1) N1 27(3) 27(2) 22(2) 2(2) 9(2) 4(2) N2 22(3) 23(2) 23(2) 1(2) -3(2) -3(2) N3 23(3) 22(2) 26(2) 1(2) 3(2) -1(2) C1 19(3) 21(2) 21(3) -3(2) 2(2) -2(2) C2 26(3) 40(3) 31(3) 12(2) 10(3) 6(3) C3 38(4) 47(3) 31(3) 19(3) 5(3) 1(3) C4 32(4) 33(3) 31(3) 3(2) 0(3) 4(3) C5 25(3) 50(3) 30(3) 1(3) 8(3) 11(3) C6 30(3) 40(3) 23(3) 5(2) 8(2) -2(3) C7 24(3) 25(2) 21(3) 1(2) 6(2) -3(2) C8 31(3) 27(3) 19(3) -1(2) -2(2) -5(2) C9 38(4) 28(3) 24(3) 6(2) 1(3) 0(3) C10 38(4) 23(3) 37(3) -2(2) 9(3) -5(3) C11 30(3) 32(3) 34(3) -5(2) -3(3) -5(3) C12 27(3) 28(2) 23(3) -1(2) 1(2) -3(2) C13 31(3) 29(3) 18(3) -1(2) -2(2) 1(3) C14 38(4) 33(3) 32(3) -5(3) -2(3) -1(3) C15 33(4) 24(3) 46(4) -10(2) -6(3) 1(2) C16 25(3) 29(3) 45(4) -1(3) 3(3) -6(3) C17 32(3) 25(3) 31(3) 0(2) 2(3) 0(3) 141

PAGE 142

Crystallographic Data for [iPrNC(NMe2)NiPr]Cl3WNNMe2 (28) Table A-13. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (2x 103) for 28. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) W1 2932(1) 2907(1) 2355(1) 20(1) Cl1 4302(2) 2034(2) 1313(1) 29(1) Cl2 1787(2) 3452(2) 3605(1) 31(1) Cl3 1391(2) -112(1) 2502(1) 32(1) N1 1252(5) 2913(5) 1445(3) 24(1) N2 135(6) 3063(7) 738(3) 39(1) N3 5554(5) 3629(4) 3397(2) 21(1) N4 4905(5) 5340(4) 2574(2) 22(1) N5 7989(5) 6562(4) 3585(3) 24(1) C1 -1609(10) 2795(13) 920(5) 69(2) C2 13(9) 2287(9) -178(4) 48(1) C3 6262(5) 5231(5) 3244(3) 20(1) C4 6355(6) 2999(6) 4154(3) 24(1) C5 5073(7) 2313(7) 4787(3) 34(1) C6 6697(7) 1580(6) 3732(4) 35(1) C7 5258(7) 6821(6) 2078(3) 30(1) C8 3748(9) 7295(7) 2033(4) 46(1) C9 5377(12) 6339(9) 1088(5) 62(2) C10 8301(7) 8258(6) 4007(3) 32(1) C11 9585(7) 6303(7) 3817(4) 42(1) 142

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Table A-14. Bond lengths [] and angles [] for 28. W1-N1 1.753(4) W1-N4 1.974(3) W1-N3 2.214(3) W1-Cl2 2.3745(11) W1-Cl1 2.3900(10) W1-Cl3 2.4162(11) W1-C3 2.592(4) N1-N2 1.320(6) N2-C2 1.445(7) N2-C1 1.465(7) N3-C3 1.313(5) N3-C4 1.464(5) N4-C3 1.402(5) N4-C7 1.480(5) N5-C3 1.348(5) N5-C11 1.447(6) N5-C10 1.466(6) C4-C5 1.517(6) C4-C6 1.531(6) C7-C8 1.505(7) C7-C9 1.540(8) N1-W1-N4 101.14(16) N1-W1-N3 163.40(16) N4-W1-N3 62.71(13) N1-W1-Cl2 96.94(12) N4-W1-Cl2 92.71(11) N3-W1-Cl2 88.10(9) N1-W1-Cl1 93.50(12) N4-W1-Cl1 91.22(11) N3-W1-Cl1 83.56(9) Cl2-W1-Cl1 167.92(4) N1-W1-Cl3 99.67(13) N4-W1-Cl3 159.10(11) N3-W1-Cl3 96.40(9) Cl2-W1-Cl3 86.72(4) Cl1-W1-Cl3 85.54(4) N1-W1-C3 133.28(15) N4-W1-C3 32.29(13) N3-W1-C3 30.43(12) Cl2-W1-C3 90.77(9) 143

PAGE 144

Table A-14. continued. Cl1-W1-C3 86.46(9) Cl3-W1-C3 126.81(9) N2-N1-W1 173.8(4) N1-N2-C2 115.8(4) N1-N2-C1 113.9(5) C2-N2-C1 116.2(5) C3-N3-C4 126.2(4) C3-N3-W1 90.9(2) C4-N3-W1 141.7(3) C3-N4-C7 124.2(3) C3-N4-W1 98.9(2) C7-N4-W1 135.1(3) C3-N5-C11 122.3(4) C3-N5-C10 120.7(4) C11-N5-C10 114.5(4) N3-C3-N5 129.4(4) N3-C3-N4 107.4(3) N5-C3-N4 123.0(3) N3-C3-W1 58.6(2) N5-C3-W1 170.8(3) N4-C3-W1 48.79(18) N3-C4-C5 110.1(4) N3-C4-C6 109.2(4) C5-C4-C6 110.8(4) N4-C7-C8 110.0(4) N4-C7-C9 109.5(4) C8-C7-C9 110.6(5) 144

PAGE 145

Table A-15. Anisotropic displacement parameters (2x 103) for 28. The anisotropic displacement factor expo nent takes the form: -2 2[ h2 a*2U11 + ... + 2 h k a* b* U12 ] U11 U22 U33 U23 U13 U12 W1 16(1) 23(1) 19(1) 6(1) 4(1) 9(1) Cl1 28(1) 37(1) 26(1) 5(1) 12(1) 16(1) Cl2 31(1) 40(1) 29(1) 5(1) 12(1) 21(1) Cl3 33(1) 24(1) 34(1) 8(1) 14(1) 8(1) N1 14(2) 34(2) 21(2) 2(1) 2(1) 10(1) N2 29(2) 63(3) 30(2) 10(2) 3(2) 29(2) N3 19(2) 22(2) 22(2) 8(1) 3(1) 10(1) N4 20(2) 19(2) 23(2) 6(1) 0(1) 8(1) N5 20(2) 20(2) 27(2) 6(1) 4(1) 7(1) C1 42(4) 126(7) 56(4) 16(4) 11(3) 55(4) C2 50(3) 63(4) 29(3) 3(2) 1(2) 31(3) C3 20(2) 21(2) 18(2) 5(1) 3(1) 10(2) C4 26(2) 24(2) 21(2) 11(2) 4(2) 12(2) C5 37(3) 37(2) 28(2) 15(2) 10(2) 17(2) C6 38(3) 33(2) 44(3) 17(2) 12(2) 24(2) C7 33(2) 26(2) 29(2) 15(2) 6(2) 14(2) C8 52(3) 36(3) 58(3) 19(2) 7(3) 29(3) C9 97(6) 56(4) 58(4) 39(3) 44(4) 43(4) C10 41(3) 19(2) 28(2) 1(2) 12(2) 6(2) C11 20(2) 40(3) 63(4) 28(3) 7(2) 11(2) 145

PAGE 146

Crystallographic Data for [TMEDA]Li{iPrNC[N(SiMe3)2]NiPr} (32) Table A-16. Atomic coordinates ( x 104) and equivalent isotropic displacement parameters (2x 103) for 32. U(eq) is defined as one third of the trace of the orthogonalized Uij tensor. x y z U(eq) Li1 7558(2) -2962(3) 5571(2) 31(1) Si1 8402(1) -6595(1) 7093(1) 37(1) Si2 6268(1) -6313(1) 7095(1) 32(1) N1 7417(1) -4918(2) 5658(1) 29(1) N2 7486(1) -3484(2) 6562(1) 28(1) N3 7365(1) -5855(2) 6832(1) 26(1) N4 6734(1) -1557(2) 5034(1) 42(1) N5 8691(1) -2037(2) 5110(1) 42(1) C1 7422(1) -4732(2) 6343(1) 23(1) C2 7300(2) -6213(2) 5331(1) 34(1) C3 6514(2) -6144(3) 4782(1) 55(1) C4 8180(2) -6636(3) 4971(1) 52(1) C5 7525(1) -3112(2) 7293(1) 30(1) C6 6660(2) -2342(3) 7482(1) 49(1) C7 8365(2) -2227(3) 7442(1) 53(1) C8 8467(3) -6809(4) 8057(2) 89(1) C9 8564(2) -8302(3) 6712(2) 63(1) C10 9374(2) -5534(3) 6812(2) 57(1) C11 6089(2) -8147(3) 6982(2) 64(1) C12 5387(2) -5399(3) 6558(1) 47(1) C13 6061(2) -5944(3) 8035(1) 50(1) C14 6437(3) -591(4) 5531(2) 96(1) C15 5969(2) -2122(3) 4628(2) 65(1) C16 7403(2) -946(3) 4535(2) 72(1) C17 8327(2) -800(3) 4826(2) 66(1) C18 9470(2) -1768(3) 5603(2) 69(1) C19 9022(2) -2923(3) 4570(2) 69(1) 146

PAGE 147

Table A-17. Bond lengths [] and angles [] for 32. Li1-N1 1.975(4) Li1-N2 1.976(4) Li1-N4 2.097(4) Li1-N5 2.103(4) Li1-C1 2.320(4) Si1-N3 1.7387(16) Si1-C10 1.857(3) Si1-C8 1.860(3) Si1-C9 1.874(3) Si2-N3 1.7442(16) Si2-C12 1.860(2) Si2-C11 1.866(3) Si2-C13 1.872(2) N1-C1 1.325(2) N1-C2 1.447(2) N2-C1 1.320(2) N2-C5 1.449(2) N3-C1 1.468(2) N4-C14 1.431(4) N4-C15 1.453(3) N4-C16 1.512(4) N5-C17 1.447(3) N5-C19 1.454(3) N5-C18 1.478(3) C2-C4 1.528(3) C2-C3 1.532(3) C2-H2A 1 C3-H3A 0.98 C3-H3B 0.98 C3-H3C 0.98 C4-H4A 0.98 C4-H4B 0.98 C4-H4C 0.98 C5-C6 1.525(3) C5-C7 1.528(3) C5-H5A 1 C6-H6A 0.98 C6-H6B 0.98 C6-H6C 0.98 C7-H7A 0.98 147

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Table A-17. continued. C7-H7B 0.98 C7-H7C 0.98 C8-H8A 0.98 C8-H8B 0.98 C8-H8C 0.98 C9-H9A 0.98 C9-H9B 0.98 C9-H9C 0.98 C10-H10A 0.98 C10-H10B 0.98 C10-H10C 0.98 C11-H11A 0.98 C11-H11B 0.98 C11-H11C 0.98 C12-H12A 0.98 C12-H12B 0.98 C12-H12C 0.98 C13-H13A 0.98 C13-H13B 0.98 C13-H13C 0.98 C14-H14A 0.98 C14-H14B 0.98 C14-H14C 0.98 C15-H15A 0.98 C15-H15B 0.98 C15-H15C 0.98 C16-C17 1.445(4) C16-H16A 0.99 C16-H16B 0.99 C17-H17A 0.99 C17-H17B 0.99 C18-H18A 0.98 C18-H18B 0.98 C18-H18C 0.98 C19-H19A 0.98 C19-H19B 0.98 C19-H19C 0.98 N1-Li1-N2 69.40(12) N1-Li1-N4 130.32(18) N2-Li1-N4 127.15(18) 148

PAGE 149

Table A-17. continued. N1-Li1-N5 123.76(18) N2-Li1-N5 125.67(17) N4-Li1-N5 86.63(14) N1-Li1-C1 34.78(8) N2-Li1-C1 34.62(8) N4-Li1-C1 140.12(17) N5-Li1-C1 133.24(17) N3-Si1-C10 109.35(10) N3-Si1-C8 110.75(12) C10-Si1-C8 109.64(17) N3-Si1-C9 113.16(11) C10-Si1-C9 107.67(13) C8-Si1-C9 106.16(16) N3-Si2-C12 109.30(9) N3-Si2-C11 110.50(11) C12-Si2-C11 109.17(14) N3-Si2-C13 113.53(10) C12-Si2-C13 108.00(12) C11-Si2-C13 106.22(13) C1-N1-C2 123.50(16) C1-N1-Li1 86.98(14) C2-N1-Li1 149.47(16) C1-N2-C5 123.43(16) C1-N2-Li1 87.09(14) C5-N2-Li1 149.33(16) C1-N3-Si1 116.51(12) C1-N3-Si2 117.00(11) Si1-N3-Si2 126.49(9) C14-N4-C15 112.3(2) C14-N4-C16 111.0(3) C15-N4-C16 108.2(2) C14-N4-Li1 107.75(19) C15-N4-Li1 114.75(19) C16-N4-Li1 102.37(17) C17-N5-C19 112.3(2) C17-N5-C18 110.5(2) C19-N5-C18 107.8(2) C17-N5-Li1 104.59(18) C19-N5-Li1 107.95(18) C18-N5-Li1 113.88(18) 149

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Table A-17. continued. N2-C1-N1 116.50(16) N2-C1-N3 121.75(15) N1-C1-N3 121.74(16) N2-C1-Li1 58.28(12) N1-C1-Li1 58.24(12) N3-C1-Li1 178.37(15) N1-C2-C4 110.75(17) N1-C2-C3 109.49(18) C4-C2-C3 108.51(19) N1-C2-H2A 109.4 C4-C2-H2A 109.4 C3-C2-H2A 109.4 C2-C3-H3A 109.5 C2-C3-H3B 109.5 H3A-C3-H3B 109.5 C2-C3-H3C 109.5 H3A-C3-H3C 109.5 H3B-C3-H3C 109.5 C2-C4-H4A 109.5 C2-C4-H4B 109.5 H4A-C4-H4B 109.5 C2-C4-H4C 109.5 H4A-C4-H4C 109.5 H4B-C4-H4C 109.5 N2-C5-C6 110.44(17) N2-C5-C7 109.80(17) C6-C5-C7 108.73(19) N2-C5-H5A 109.3 C6-C5-H5A 109.3 C7-C5-H5A 109.3 C5-C6-H6A 109.5 C5-C6-H6B 109.5 H6A-C6-H6B 109.5 C5-C6-H6C 109.5 H6A-C6-H6C 109.5 H6B-C6-H6C 109.5 C5-C7-H7A 109.5 C5-C7-H7B 109.5 H7A-C7-H7B 109.5 C5-C7-H7C 109.5 150

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Table A-17. continued. H7A-C7-H7C 109.5 H7B-C7-H7C 109.5 Si1-C8-H8A 109.5 Si1-C8-H8B 109.5 H8A-C8-H8B 109.5 Si1-C8-H8C 109.5 H8A-C8-H8C 109.5 H8B-C8-H8C 109.5 Si1-C9-H9A 109.5 Si1-C9-H9B 109.5 H9A-C9-H9B 109.5 Si1-C9-H9C 109.5 H9A-C9-H9C 109.5 H9B-C9-H9C 109.5 Si1-C10-H10A 109.5 Si1-C10-H10B 109.5 H10A-C10-H10B 109.5 Si1-C10-H10C 109.5 H10A-C10-H10C 109.5 H10B-C10-H10C 109.5 Si2-C11-H11A 109.5 Si2-C11-H11B 109.5 H11A-C11-H11B 109.5 Si2-C11-H11C 109.5 H11A-C11-H11C 109.5 H11B-C11-H11C 109.5 Si2-C12-H12A 109.5 Si2-C12-H12B 109.5 H12A-C12-H12B 109.5 Si2-C12-H12C 109.5 H12A-C12-H12C 109.5 H12B-C12-H12C 109.5 Si2-C13-H13A 109.5 Si2-C13-H13B 109.5 H13A-C13-H13B 109.5 Si2-C13-H13C 109.5 H13A-C13-H13C 109.5 H13B-C13-H13C 109.5 N4-C14-H14A 109.5 N4-C14-H14B 109.5 151

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Table A-17. continued. H14A-C14-H14B 109.5 N4-C14-H14C 109.5 H14A-C14-H14C 109.5 H14B-C14-H14C 109.5 N4-C15-H15A 109.5 N4-C15-H15B 109.5 H15A-C15-H15B 109.5 N4-C15-H15C 109.5 H15A-C15-H15C 109.5 H15B-C15-H15C 109.5 C17-C16-N4 113.6(2) C17-C16-H16A 108.8 N4-C16-H16A 108.8 C17-C16-H16B 108.8 N4-C16-H16B 108.8 H16A-C16-H16B 107.7 C16-C17-N5 112.6(2) C16-C17-H17A 109.1 N5-C17-H17A 109.1 C16-C17-H17B 109.1 N5-C17-H17B 109.1 H17A-C17-H17B 107.8 N5-C18-H18A 109.5 N5-C18-H18B 109.5 H18A-C18-H18B 109.5 N5-C18-H18C 109.5 H18A-C18-H18C 109.5 H18B-C18-H18C 109.5 N5-C19-H19A 109.5 N5-C19-H19B 109.5 H19A-C19-H19B 109.5 N5-C19-H19C 109.5 H19A-C19-H19C 109.5 H19B-C19-H19C 109.5 152

PAGE 153

153 Table A-18. Anisotropic displacement parameters (2x 103) for 32. The anisotropic displacement factor expo nent takes the form: -2 2[ h2 a*2U11 + ... + 2 h k a* b* U12 ] U11 U22 U33 U23 U13 U12 Li1 33(2) 32(2) 27(2) 1(1) 1(1) -2(1) Si1 40(1) 38(1) 33(1) 2(1) -7(1) 11(1) Si2 36(1) 31(1) 29(1) -2(1) 6(1) -7(1) N1 38(1) 26(1) 22(1) -2(1) 0(1) -2(1) N2 37(1) 25(1) 21(1) -2(1) 1(1) -2(1) N3 29(1) 25(1) 23(1) 1(1) -1(1) 0(1) N4 45(1) 40(1) 40(1) -3(1) -13(1) 3(1) N5 43(1) 44(1) 39(1) 4(1) 8(1) -9(1) C1 21(1) 26(1) 24(1) 1(1) 0(1) 0(1) C2 46(1) 29(1) 26(1) -5(1) 1(1) -3(1) C3 61(2) 58(2) 45(1) -21(1) -13(1) -5(1) C4 60(2) 48(1) 48(1) -18(1) 8(1) 8(1) C5 42(1) 27(1) 22(1) -3(1) 1(1) -3(1) C6 58(2) 55(2) 35(1) -11(1) 6(1) 9(1) C7 61(2) 55(2) 42(1) -19(1) -2(1) -18(1) C8 90(2) 133(3) 41(2) 13(2) -14(2) 51(2) C9 67(2) 39(1) 84(2) 0(1) -4(2) 18(1) C10 31(1) 57(2) 83(2) -8(1) -5(1) 7(1) C11 72(2) 38(1) 84(2) -8(1) 28(2) -19(1) C12 29(1) 67(2) 46(1) -2(1) 1(1) -6(1) C13 55(2) 60(2) 34(1) 0(1) 13(1) -6(1) C14 116(3) 89(3) 81(2) -31(2) -26(2) 55(2) C15 49(2) 82(2) 64(2) 1(2) -19(1) -12(1) C16 79(2) 67(2) 68(2) 37(2) -12(2) -9(2) C17 65(2) 55(2) 77(2) 27(2) 10(2) -6(1) C18 60(2) 82(2) 64(2) 2(2) -5(1) -25(2) C19 58(2) 93(2) 58(2) -15(2) 21(1) -4(2)

PAGE 154

APPENDIX B NMR KINETICS DAT A FOR COMPOUND 24 Table B-1. Rates for acetoni trile exchange in compound 24. T (C) k (sec-1) 1/T ln(k/T) 40 0 0.003193 --42 1.46 0.003173 -5.374644 44 3.23 0.003153 -4.586924 46 5.32 0.003133 -4.094219 48 7.99 0.003114 -3.693749 50 9.9 0.003094 -3.485613 52 13.3 0.003075 -3.196553 54 16.9 0.003057 -2.963136 56 21.3 0.003038 -2.737837 58 27.6 0.003020 -2.484786 60 33.9 0.003002 -2.285208 62 41.3 0.002984 -2.093746 64 50.4 0.002966 -1.900566 66 59.3 0.002948 -1.743863 68 71.4 0.002931 -1.564054 70 84.7 0.002914 -1.399081 72 104 0.002897 -1.199617 74 125 0.002881 -1.021472 76 153 0.002864 -0.825092 78 186 0.002848 -0.635495 80 230 0.002832 -0.428842 82 279 0.002816 -0.241357 84 339 0.002800 -0.052184 154

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BIOGRAPHICAL SKETCH Jrgen Koller was born in 1981, in Regensburg, Germany. His interest in science started emerging at the local high school in Parsberg, Germany, under the guidance of a local chemistry teacher, Dr. Beate Panzer. After completing 10 months of mandatory military service, he began his studies in the field of general chemistry at the Universitt Regensburg, Germany, where Prof. Henri Brunner sparked his interest for organomet allic chemistry. After receiving his Vordiplom, he transferred to the University of Florida, Gainesville, Florida, and began his graduate studies under the supervision of Prof. Adam Veige. There he spent the next two years studying organometallic compounds. In September 2006 he joined the research group of Prof. Lisa McElwee-White where he continued exploring the world of organometallic chemistry until receiving his Ph.D. degree in inorganic/organom etallic chemistry in th e fall of 2008. He has accepted a post-doctoral research position at the University of California, Berkeley, where he will be working on catalytic hydroamination reactions under the supervision of Dr. Robert Bergman. 165