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i Database Needs for Modeling and Simulation of Plasma Processing Panel on Database Needs in Plasma Processing Committee on Atomic, Molecular, and Optical Sciences and Plasma Science Committee Board on Physics and Astronomy Commission on Physical Sciences, Mathematics, and Applications National Research Council National Academy Press Washington, D.C. 1996
ii NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose mem- bers are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the panel responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee con- sisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineer- ing programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is interim president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an advisor to the federal government and, upon its own initia- tive, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was established by the National Academy of Sciences in 1916 to associate the broad community of sci- ence and technology with the Academy's purposes of furthering knowledge and of advising the federal government. Functioning in accor- dance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. William A. Wulf are chairman and interim vice chairman, respectively, of the National Research Council. This project was supported by the Defense Advanced Research Projects Agency and the Office of Naval Research under contract num- ber N00014-89-J-1728. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors. Cover: A plasma-etched gate 0.12 microns wide, patterned with x-ray lithography. (Courtesy of G. Rittenhouse, J.T.C. Lee, and A. Kornblit, Lucent Technologies Bell Laboratories.) Copyright 1996 by the National Academy of Sciences. All rights reserved. Library of Congress Catalog Card Number 96-70732 International Standard Book Number 0-309-05591-1 Additional copies of this report are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington, DC 20055 1-800-624-6242 or 202-334-3313 (in the Washington Metropolitan Area) http://www.nap.edu Printed in the United States of America
iii PANEL ON DATABASE NEEDS IN PLASMA PROCESSING DAVID B. GRAVES, University of California, Berkeley, Co-Chair MARK J. KUSHNER, University of Illinois at Urbana-Champaign, Co-Chair JEAN W. GALLAGHER, National Institute of Standards and Technology ALAN GARSCADDEN, Wright Laboratory GOTTLIEB S. OEHRLEIN, State University of New York at Albany ARTHUR V. PHELPS, University of Colorado, JILA Agency Liaisons BERTRAM HUI, Defense Advanced Research Projects Agency CHARLES ROBERSON, Office of Naval Research DANIEL F. MORGAN, Program Officer
iv COMMITTEE ON ATOMIC, MOLECULAR, AND OPTICAL SCIENCES WILLIAM STWALLEY, University of Connecticut, Chair WENDELL T. HILL III, University of Maryland, Vice Chair ROBERT W. FIELD, Massachusetts Institute of Technology DANIEL GRISCHKOWSKY, Oklahoma State University TONY F. HEINZ, IBM T.J. Watson Research Center PAUL S. JULIENNE, National Institute of Standards and Technology H. JEFFREY KIMBLE, California Institute of Technology SIU AU LEE, Colorado State University C. WILLIAM McCURDY, JR., Lawrence Livermore National Laboratory MARA G. PRENTISS, Harvard University DAVID J. WINELAND, National Institute of Standards and Technology PLASMA SCIENCE COMMITTEE RAVI SUDAN, Cornell University, Chair CHUAN S. LIU, University of Maryland, Vice Chair STEVEN C. COWLEY, University of California, Los Angeles VINCENT DONNELLY, AT&T Bell Laboratories ROY GOULD, California Institute of Technology RICHARD D. HAZELTINE, University of Texas at Austin WILLIAM L. KRUER, Lawrence Livermore National Laboratory MICHAEL LIEBERMAN, University of California, Berkeley GERALD L. ROGOFF, OSRAM Sylvania, Inc. NATHAN RYNN, University of California, Irvine ELLEN ZWEIBEL, University of Colorado
v BOARD ON PHYSICS AND ASTRONOMY DAVID N. SCHRAMM, University of Chicago, Chair ROBERT C. DYNES, University of California at San Diego, Vice Chair LLOYD ARMSTRONG, JR., University of Southern California DAVID H. AUSTON, Rice University IRA BERNSTEIN, Yale University PRAVEEN CHAUDHARI, IBM T.J. Watson Research Center SANDRA M. FABER, University of California at Santa Cruz HANS FRAUENFELDER, Los Alamos National Laboratory JEROME I. FRIEDMAN, Massachusetts Institute of Technology MARGARET J. GELLER, Harvard-Smithsonian Center for Astrophysics MARTHA P. HAYNES, Cornell University WILLIAM KLEMPERER, Harvard University AL NARATH, Sandia National Laboratories JOSEPH M. PROUD, GTE Corporation (retired) ANTHONY C.S. READHEAD, California Institute of Technology ROBERT C. RICHARDSON, Cornell University JOHANNA STACHEL, State University of New York at Stony Brook DAVID WILKINSON, Princeton University DONALD C. SHAPERO, Director ROBERT L. RIEMER, Associate Director DANIEL F. MORGAN, Program Officer NATASHA CASEY, Senior Administrative Associate CHRISTOPHER HANNA, Project Assistant
vi COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND APPLICATIONS ROBERT J. HERMANN, United Technologies Corporation, Co-Chair W. CARL LINEBERGER University of Colorado, Co-Chair PETER M. BANKS, Environmental Research Institute of Michigan L. LOUIS HEGEDUS, Elf Atochem North America, Inc. JOHN E. HOPCROFT, Cornell University RHONDA J. HUGHES, Bryn Mawr College SHIRLEY A. JACKSON, U.S. Nuclear Regulatory Commission KENNETH H. KELLER, Council on Foreign Relations KENNETH I. KELLERMAN, National Radio Astronomy Observatory KEN KENNEDY, Rice University DANIEL KLEPPNER, Massachusetts Institute of Technology MARSHA I. LESTER, University of Pennsylvania NICHOLAS P. SAMIOS, Brookhaven National Laboratory L.E. SCRIVEN, University of Minnesota SHMUEL WINOGRAD, IBM T.J. Watson Research Center CHARLES A. ZRAKET, MITRE Corporation (retired) NORMAN METZGER, Executive Director
PREFACE vii Preface In the spring of 1994 the Plasma Science Committee and the Committee on Atomic, Molecular, and Optical Sciences of the National Research Council (NRC) established a panel to organize and conduct a workshop on database needs in plasma processing of materials. This activity was motivated by the NRC report Plasma Processing of Materials: Scientific Opportunities and Technological Challenges (National Academy Press, Washington, D.C., 1991), prepared by the Panel on Plasma Processing and Materials under the auspices of the Board on Physics and Astronomy, which pointed out the need for an improved database to enable more quantitative modeling of plasma reactors and processes, especially in the area of integrated circuit manufacturing. The beneficial product of such modeling would be a more competitive and responsive microelectronics industry that serves both defense and civilian markets. The primary purpose of the workshop, held April 1 and 2, 1995, in Washington, D.C., was to bring together experts with the goal of developing a prioritized list of database and diagnostic needs based on their potential impact on plasma processing technology. This report summarizes the findings of the workshop. Each of the members of the Panel on Database Needs in Plasma Processing headed an ad hoc group that helped draft a subset of the report, based on input from the workshop participants. The panel thanks the members of these groups for their assistance: P.B. Armentrout, University of Utah; E. Aydil, University of California, Santa Barbara; K.H. Becker, The City College of the City University of New York; R. Buss, Sandia National Laboratories; M.W. Chase, National Institute of Standards and Technology; L.G. Christophorou, Oak Ridge National Laboratory; J.M. Cook, Lain Research Corporation; D. Ernie, University of Minnesota; K.P. Giapis, California Institute of Technology; M.F. Golde, University of Pittsburgh; I.P. Herman, Columbia University; P. Ho, Sandia National Laboratories; R. Johnsen, University of Pittsburgh; Y.-K. Kim, National Institute of Standards and Technology; H. Sawin, Massachusetts Institute of Technology; D.W. Setser, Kansas State University; S. Srivastava, Jet Propulsion Laboratory; W. Tsang, National Institute of Standards and Technology; R.J. Van Brunt, National Institute of Standards and Technology; C. Woods, University of Wisconsin; J. Wormhoudt, Aerodyne Research Inc.; and M. Zachariah, National Institute of Standards and Technology. In view of the fact that the primary use of data on plasma processing is in technology development in industry, special efforts were made to ensure that there was extensive industrial participation in the workshop, both in breadth and depth. The panel owes a particular debt of gratitude to the following individuals for their active participation in the workshop and for critiquing and improving drafts of the report: Kaihan A. Ashtiani of Materials Research Corporation; Andrew D. Bailey HI of Plasma and Materials Technologies; Joel M. Cook of Lam Research Corporation; Frederick Dill of IBM T.J. Watson Research Center; Vincent Donnelly of Lucent Technologies Bell Laboratories; Erik Egan of Motorola; Sychi Fang of Intel Corporation; David Fraser of Intel Corporation; Abe Ghanbari of Materials Research Corporation; R.A. Gottscho of Lain Research Corporation (formerly of AT&T Bell Laboratories); Michael Hartig of Motorola/Sematech; Les Jerde of Tegal Corporation; Andrew Labun of Digital Equipment Corporation; Michael Mocella of Dupont; Joseph Proud of GTE; Vivek Singh of Intel Corporation; Vikram Singh of Lam Research Corporation; M. Surendra of IBM T.J. Watson Research Center; Alexander Voschenkov of Lain Research Corporation; and Jody Wormhoudt of Aerodyne Research. The scope of this report is substantial, covering industrial needs for better plasma process engineering, the current state of the art in plasma modeling, and the various supporting databases and diagnostics techniques that underlie and complement modeling and simulation. The report is intended for a variety of audiences: academic and government laboratory researchers, industrial engineers and scientists, and technical program managers at federal agencies. Although it emphasizes industrial and technological applications, the report raises many challenging questions involving fundamental science that underlies the
PREFACE viii technological applications, and these challenges should appeal to many in the basic science community as well as to technologists. The fundamental science disciplines to which this report is most relevant include, but are not limited to, plasma science and atomic, molecular, and optical science. The panel notes that this report has been preceded by several excellent reports that address similar and/or complementary issues from somewhat different perspectives. The Semiconductor Industry Association (SIA), for example, prepares periodic "roadmaps" of industrial needs and potential solutions to guide technology development in critical areas of semiconductor manufacturing. SIA's second such report (The National Technology Roadmap for Semiconductors, SEMATECH, Austin, Tex., 1994) contains numerous insights regarding the role of future plasma processing in semiconductor manufacturing. In 1995 SEMATECH published an important supplement to the SIA roadmap; titled Technology Computer-Aided Design (TCAD) Roadmap: Supplement to the National Technology Roadmap for Semiconductors, it contains a chapter on equipment modeling, including plasma equipment modeling and the database needs for this application. In 1994 SEMATECH published White Paper for a Chemical Kinetics Database to Support Integrated Circuit Manufacture, a report that focuses primarily on modeling and simulation for thermal chemical vapor deposition (CVD) processes and that contains much useful information and valuable insight on the proper approach to developing an equipment modeling database. As noted above, plasma processing was specifically addressed in the 1991 NRC report Plasma Processing of Materials, which provided the primary motivation for the present activity. In 1995, the NRC published in the Naval Research Laboratory Series a report titled Plasma Processing and Processing Science (National Academy Press, Washington, D.C.). Also published in 1995 was a comprehensive NRC report entitled Plasma Science: From Fundamental Research to Technological Applications (National Academy Press, Washington, D.C.). All of these previously published reports contain useful, often additional, and sometimes conflicting information relevant to the goals of this report. Readers are advised to examine the earlier reports as well, to obtain historical perspective and a broader base of opinion.
CONTENTS ix Contents Executive Summary 1 Findings 1 Conclusions 2 Recommendations 3 References 4 1 Industrial Perspectives 5 Introduction 5 Plasma Processing for Semiconductor Manufacturing 5 Plasma Equipment Supplier Perspectives 8 Chip Manufacturer Perspectives 9 Recommended Priorities for Development of an Improved Database 11 Findings 12 Conclusions 12 References 12 2 Tool Scale and Feature Scale Models 13 Introduction 13 Tool Scale Models 13 Capabilities Needed for Tool Scale Models 15 Barriers to Using Tool Scale Models 15 Feature Scale Models 16 General Assessment of Modeling State of the Art and Vision of Future Capability and Implied Needs 17 Findings 21 Conclusions 21 References 21 3 Radiative Processes and Diagnostics 23 Introduction 23 Techniques for Measurements of Gas Phase Species 23 Information Resources 24 Roles of the Database in Motivating Diagnostic Experiments 25 Surface Reaction Database and Diagnostics 26 Information Resources 27 New Diagnostic Techniques 27 Findings 28 References 29 4 Heterogeneous Processes 33 Introduction 33 State of the Database 33 Techniques for Improving the Database 34 Approach 34 Measurements on Realistic Plasma Reactors 34 Incident Flux and Desorbing Flux Analysis 34
CONTENTS x Condition of the Surface 35 Technology 36 Ultrahigh-Vacuum Approach Using Mass and Energy Selected Reactive Beams 36 Particle Beams 36 Sticking Coefficients 37 Synergistic Effects 37 Substrate Temperature Dependence 37 Angle Dependence 38 Computer Simulations 38 Findings 38 References 38 5 Electron Collision Processes 41 Introduction 41 Ionization 41 Atoms 41 Molecules 41 Theoretical Methods and Advances 42 Neutral Dissociation 42 Electron-Impact Excitation 43 Attachment 43 Momentum Transfer, Swarm, and Discharge Measurements 43 General Comments 44 Findings 45 References 45 6 Ion Processes, Neutral Chemistry, and Thermochemical Data 47 Introduction 47 Cross Sections and Rate Coefficients 48 Ion Processes 48 Momentum Transfer 48 Ion-Molecule and Charge Exchange Reactions 48 Ion-Ion Neutralization 50 Electron-Ion Recombination 51 Ion-Neutral and Neutral-Neutral Excitation 51 Neutral Chemistry 51 Status of the Database 52 Excited State Chemistry and Penning Ionization 53 Summary 54 Ion Processes 55 Neutral Chemistry 55 Thermochemical Data 55 Findings 57 References 57 Appendix A: Acronyms and Abbreviations 59 Appendix B: Workshop Agenda 61 Appendix C: Workshop Participants 63