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Copyright by Brian C. Trinque 2003 The Dissertation Committee for Brian C. Trinque Certifies that this is the approved version of the following dissertation: SYNTHESIS, COPOLYMERIZATION STUDIES AND 157 nm PHOTOLITHOGRAPHY APPLICATIONS OF 2-TRIFLUOROMETHYLACRYLATES Committee: C. Grant Willson, Supervisor Brent L. Iverson Hiroshi Ito Michael J. Krische Stephen E. Webber SYNTHESIS, COPOLYMERIZATION STUDIES AND 157 nm PHOTOLITHOGRAPHY APPLICATIONS OF 2-TRIFLUOROMETHYLACRYLATES by Brian C. Trinque, B.A. Dissertation Presented to the Faculty of the Graduate School of The University of Texas at Austin in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy The University of Texas at Austin May, 2003 For AKT Acknowledgements First and foremost, I am most indebted to my research advisor, Professor Grant Willson. I thank him for giving me the opportunity and support to study chemistry in his research group. I am also grateful for the encouragement and guidance of Dr. Peter Tattersall, who first taught me the majority of the chemistry laboratory skills required to perform the experiments in this dissertation. I also acknowledge Dr. Hiroshi Ito, whom, through the help of Professor Willson, I worked with at the IBM Almaden Research Center in the summer of 2003. I learned a great deal during this collaboration. I must also thank my fellow colleagues in the Willson Group for their assistance with the contents of this dissertation. I remember times when I thought that, due to periods of no success, my graduate career would come to a screeching halt. However, it was during these times that both Matthew Pinnow and Takashi Chiba successfully synthesized molecules that breathed new life into my research. I also thank two undergraduate researchers who were a pleasure to work with: Jennifer Wunderlich and Schuyler Corry. I thank Dr. Colin Brodsky and Brian Osborn for help with acquiring all of the gas phase data shown on these pages. I am also fortunate to have had a chance to do research with Sean Burns, Michael Stewart, Gerard Schmid, Heather Johnson, and EK Kim. I am grateful for many helpful discussions with Charles Chambers, Will Conley, Dr. Ryan Callahan, Dr. Thomas Mrozek, Shiro Kusumoto, Dr. Dave Johnson, Dr. Raymond Hung, Dr. H.V. Tran, Bill Heath, Stefan Caporale, and Dr. Scott Grayson. I must also not v forget the assistance that Kathleen Sparks has given me over the years. I am certain that I would not have graduated when I did without the help of all of those mentioned above. Finally, I must thank Anne for her love, patience, and endless support. vi SYNTHESIS, COPOLYMERIZATION STUDIES AND 157 nm PHOTOLITHOGRAPHY APPLICATIONS OF 2-TRIFLUOROMETHYLACRYLATES Publication No._____________ Brian C. Trinque, Ph. D. The University of Texas at Austin, 2003 Supervisor: C. Grant Willson Advances in microelectronic devices have relied heavily on improved photolithographic imaging capabilities. The resolution limit of optical lithography can be improved by lowering the wavelength of exposure light. The latest reduction in exposure wavelength is from 193 nm to 157 nm. The focus of this work is the synthesis, copolymerization studies and lithographic imaging capabilities of 2-trifluoromethylacrylates. Model calculations and gas phase absorbance measurements of model compounds first suggested that these materials would provide suitable transparency at the 157 nm wavelength. Methyl 2-trifluoromethylacrylate was synthesized and aniocically polymerized and variable angle spectroscopic ellipsometry showed that this material had an vii absorbance that was 1,000 times more transparent than its non-fluorinated analogue. A variety of relatively transparent resist materials based on a 2- trifluoromethylacrylate backbone were synthesized by anionic polymerization, and these materials were successfully imaged at 157 nm. While 2- trifluoromethylacrylates do not undergo homopolymerization with radical initiators, they do radically copolymerize with various norbornenes. Interestingly, these materials exhibit a 2:1 (2-trifluromethacrylate:norbornene) monomer incorporation. This phenomenon was exploited to produce a number of relatively transparent materials that produced positive-tone structures when imaged at the 157 nm wavelength. Kinetic studies were performed to show that the copolymerizations of 2-trifluormethacrylates and norbornene derivatives deviate from the terminal model and follow the penultimate model. Competitive reaction studies using the “mercury method” were performed to demonstrate that substitution of a trifluoromethyl group can indeed effect the reactivity of a propagating radical, lending support to the proposed penultimate model. The structure of the 2-trifluoromethylacrylate propagating radical will also be investigated by electron spin resonance spectroscopy. viii Table of Contents List of Tables .........................................................................................................xii List of Figures...................................................................................................... xiii CHAPTER 1: INTRODUCTION............................................................................1 Moore’s Law...................................................................................................1 Microlithography............................................................................................2 Formulation, Spin-Coat and Post Apply Bake ...............................................3 Exposure and Post Exposure Bake .................................................................3 Development, Etch and Strip..........................................................................4 Resolution limit of optical lithography...........................................................4 Novolac/Diazonapthoquinone Resist Systems ...............................................6 Chemically Amplified Resists and the Photoacid Generator .........................7 The Onishi Paramater .....................................................................................9 Resist Transparency......................................................................................10 Photoresists for 193 nm Lithography ...........................................................11 Airborne Amine Contamination and Base Additives ...................................14 CHAPTER 2: DEVELOPMENT OF A RESIST POLYMER FOR 157 nm PHOTOLITHOGRPHY ...............................................................................16 The Advent of 157 nm Microlithography.....................................................16 Polymer Absorbances at 157 nm..................................................................16 Vacuum-UV Studies.....................................................................................18 Absorbances of Fluroinated Norbornanes: 2,2-Difluoronorbornane and 2-Fluoronorbornane .............................................................................19 7,7-Difluoronorbornane................................................................................20 7-Fluoronorbornane ......................................................................................22 V-UV Absorbances of Fluorinated Norbornanes .........................................27 The Hexafluoroisopropanol Group...............................................................28 ix Modeling Studies of the Effect of Fluorine Substitution..............................30 V-UV Studies of Fluorinated Esters.............................................................31 CHAPTER 3: 2-TRIFLUOROMETHYLACRYLATES AS BACKBONES FOR 157 nm PHOTORESIST POLYMERS ...............................................35 Methyl 2-Trifluoromethylacrylate Reactivity ..............................................35 Synthesis of Poly(Methyl 2-Trifluoromethylacrylate) .................................37 Esters of 2-Trifluoromethylacrylate .............................................................40 A 157 nm Resist Polymer with a 2-Trifluoromethylacrylate Backbone ......43 157 nm Imaging............................................................................................44 An Etch Resistant 2-Trifluoromethylacrylate Resist Polymer .....................46 Polymer Synthesis ........................................................................................48 157 nm Imaging............................................................................................49 Radical Copolymerizations of 2-trifluoromethylacrylate and Norbornene..51 Application of Gas Phase Studies.................................................................52 Other Fluorinated Norbornanes ....................................................................53 Novel 2-Trifluoromethylacrylates ................................................................55 Radical Copolymers .....................................................................................56 Investigation of Polymer Solubility..............................................................60 The Carboxylic Acid Moiety to Increase Base Solubility............................62 157 nm Imaging............................................................................................64 Acetal Protecting Group ...............................................................................65 157 nm Imaging............................................................................................66 CHAPTER 4: REACTIVITY STUDEIS OF 2-TRIFLUROMETHYL ACRYLATES TOWARD RADICAL POLYMERIZATIONS...................69

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