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Fluorocarbon Post-Etch Residue Removal Using Radical Anion Chemistry

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Fluorocarbon Post-Etch Residue Removal Using Radical Anion Chemistry FLUOROCARBON POST-ETCH RESIDUE REMOVAL USING RADICAL ANION CHEMISTRY A Thesis Presented to the Academic Faculty by Christopher L. Timmons In Partial Fulfillment of the Requirements of the degree Doctor of Philosophy in Chemical Engineering Georgia Institute of Technology November 2004 FLUOROCARBON POST-ETCH RESIDUE REMOVAL USING RADICAL ANION CHEMISTRY Approved: Dr. Dennis Hess, Chairman Dr. Carson Meredith School of Biomolecular & Chemical Engineering School of Biomolecular & Chemical Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Paul Kohl Dr. Joseph Schork School of Biomolecular & Chemical Engineering School of Biomolecular & Chemical Engineering Georgia Institute of Technology Georgia Institute of Technology Dr. Charles Liotta School of Biomolecular & Chemical Engineering and School of Chemistry and Biochemistry Date Approved: Georgia Institute of Technology November 22, 2004 ACKNOWLEDGEMENTS I would like to gratefully acknowledge my thesis advisor, Professor Dennis Hess, for his guidance, enthusiasm and support during my studies. He has instilled in me an appreciation for science and creativity in research that I hope is reflected in this work. I would also like to thank my committee members, Dr. Charles Liotta, Dr. Paul Kohl, Dr. Carson Meredith and Dr. Joseph Schork, for their insightful suggestions, feedback and critique of my work. The generous use of equipment and training provided by the research groups of Dr. Paul Kohl, Dr. Cliff Henderson, Dr. Lawrence Bottomley, Dr, Jiri Janata, Dr. Charles Eckert, and Dr. Jack Winnick were essential for my success throughout my research. I wish to thank the current and past members of my research group for providing a stimulating and fun environment including Dr. Galit Levitin, Dr. Satya Myneni, Dr. Matthew Spuller, Dr. Jie Diao, Ingu Song, Gelareh Shakourian, Qian Luo, Sudeep Vaswani and Prabhakar Tamirisa. I am indebted to Galit and Satya for advice, technical discussions and support. I have enjoyed their close friendship. I also appreciate the numerous samples processed by Jie and Sudeep. I will miss the countless conversations where I learned about different backgrounds and cultures as well as learned much about myself. I appreciate the friendship and support from the many friends I have made here; there are too many to list. I would especially like to thank Chris Moore and Cody Berger and their iii families for helping me keep my sanity during this journey. Both were always selfless, honest and loyal and I could not ask for better friends. I also appreciate the friendships of Matt Spuller, Beckie Jones and Hollie Kelleher. I wish to thank my parents for their advice and support, both emotional and financial, throughout graduate school. They are responsible for the person I am today. I would also like to thank the MiRC and CHBE staff, especially Gloria Beale, Rod Sefton and Scott Fowler. Finally, I would like to thank my wife, to whom I dedicate this accomplishment, for her never ending support, patience and motivation. I could not have done it without her. Partial finanical support for this project was provided by Air Products and Chemicals, Inc. and the GAANN fellowship (provided through Professor Peter Hesketh). iv TABLE OF CONTENTS ACKNOWLEDGEMENTS...............................................................................................iii LIST OF TABLES.............................................................................................................. x LIST OF FIGURES .......................................................................................................... xii CHAPTER 1 .......................................................................................................................1 1.1 Integrated Circuit Scaling ....................................................................................... 1 1.2 New Material Integration........................................................................................ 4 1.3 Dissertation Overview ............................................................................................ 6 CHAPTER 2 BACKGROUND AND LITERATURE REVIEW ..................................... 9 2.1 Integrated Circuit Overview ................................................................................... 9 2.1.1 Back-end-of-line integrated circuit fabrication............................................... 9 2.1.2 Drivers in the semiconductor industry and low-k material integration ........ 12 2.2 Fluorocarbon Residue Generation During Plasma Etching.................................. 15 2.2.1 Principles of plasma etching ......................................................................... 15 2.2.2 Fluorocarbon plasma etching of silicon dioxide........................................... 17 2.2.3 Fluorocarbon post-etch residue characterization .......................................... 19 2.2.4 Fluorocarbon post-etch residue generation while etching low-k materials .. 21 2.3 Fluorocarbon Residue Removal............................................................................ 22 2.3.1 Conventional fluorocarbon cleaning techniques........................................... 22 2.3.2 Low-k cleaning compatibility....................................................................... 26 2.3.3 Emerging BEOL cleaning technologies........................................................ 27 2.4 Radical Anion Chemistry...................................................................................... 29 2.4.1 Surface modification of fluorocarbon surfaces............................................ 29 2.4.2 Background on radical anion chemistry ....................................................... 36 v 2.4.3 Generation techniques for radical anions...................................................... 42 2.5 Aqueous Ozone..................................................................................................... 44 2.5.1 Chemistry of aqueous ozone......................................................................... 44 2.5.2 IC processing using aqueous ozone .............................................................. 50 2.6 Opportunities ........................................................................................................ 52 CHAPTER 3 MATERIALS AND EXPERIMENTAL METHODS............................... 53 3.1 Chemicals and Purification................................................................................... 53 3.2 Equipment and Experimental Techniques ............................................................ 53 3.2.1 X-ray photoelectron spectroscopy ................................................................ 53 3.2.2 Spectroscopic ellipsometry ........................................................................... 56 3.2.3 Atomic absorption spectrometry................................................................... 57 3.2.4 Fourier transform infrared spectroscopy....................................................... 57 3.2.5 Thin film spinning......................................................................................... 58 3.2.6 Potentiostat.................................................................................................... 58 3.2.7 1H nuclear magnetic resonance spectroscopy................................................... 58 3.2.8 Dry Box/Purge Box....................................................................................... 58 3.2.9 Contact angle measurement system.............................................................. 59 3.3 Samples................................................................................................................. 59 3.3.1 APCI Samples............................................................................................... 59 3.3.2 Dielectric material samples........................................................................... 60 3.3.3 Patterned Etch Residue Samples................................................................... 60 3.3.4 Polytetrafluoroethylene (PTFE).................................................................... 61 3.3.5 Teflon AF...................................................................................................... 61 3.4 Chemical Treatments of Samples ......................................................................... 62 3.4.1 Generation of naphthalene radical anion using sodium................................ 62 vi 3.4.2 Thin film exposure to sodium radical anions................................................ 62 3.4.3 Ozone treatments .......................................................................................... 63 3.4.4 Thin film exposure by ‘drop’ treament......................................................... 63 3.5 Electochemical Cells and Procedures ................................................................... 64 3.5.1 Reference electrode....................................................................................... 64 3.5.2 Thin film cell................................................................................................. 65 3.5.3 Dip probe cell................................................................................................ 68 3.5.4 UV-visible spectroscopy with dip probe....................................................... 70 3.5.5 Dip probe measurements............................................................................... 71 CHAPTER 4 FLUOROCARBON MODEL RESIDUE CHARACTERIZATION ........ 73 4.1 Overview..............................................................................................................
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