Principles Of Lithography, Third Edition (SPIE ...

9 PREFACE TO THE SECOND EDITION This book was written to address several needs, and the revisions for the second edition were made with those original objectives in mind. First, and foremost, this book is intended to serve as an introduction to the science of microlithography for people who are unfamiliar with the subject. Most papers written for journals or conference proceedings assume that the reader is familiar with pre-existing knowledge. The same can be said for compilations of chapters written by experts who are providing their colleagues and peers with useful summaries of the current state of the art and of the existing literature. Such papers and books, while quite useful to experienced lithographers, are not intended to address the needs of students, who first need to understand the foundations on which the latest advances rest. It is the intention of this book to fill that need. For the experienced lithographer, there are many excellent books written on specialized topics, such as photoresist and resolution enhancement techniques, and I have referenced many of those fine works. However, I have often felt that several topics have not been well addressed in the past; most notably those subjects directly related to the tools we use to manufacture integrated circuits. Consequently, this book goes into a few subjects in depth. These include such topics as overlay, the stages of exposure tools, and light sources. Finally, this text contains numerous references. These are resources for students who want to investigate particular topics in more detail, and they provide the experienced lithography with lists of references by topic. A wise leader once told me that one of the most challenging tasks is to transform complexity to simplicity; in other words, to make apparent the forest obscured by all of the trees. I hope that I have succeeded adequately on the subjects covered in this book. Of course, simplicity should never be confused with easiness or completeness. To assist the student in recognizing these distinctions, more problems have been added to the end of each chapter. It is expected that the reader of this book will have a foundation in basic physics and chemistry. No topics will require knowledge of mathematics beyond elementary calculus. Lithography is a field in which advances proceed at a swift pace, and many new topics have been included in this second edition, commensurate with the learning that has taken place during the past few years, and several subjects are discussed in more detail. Optical proximity corrections and next-generation lithography are examples where the landscape looks quite different than it did just a few years ago. Other topics, such as immersion lithography, were ideas that few took seriously just a few years ago, yet today are considered quite mainstream. It has been my good fortune to work with a number of outstanding lithographers. In addition to the people acknowledged in the preface to the first ix

Principles of Lithography, Third Edition (SPIE ...

10 x PREFACE TO THE SECOND EDITION edition, I would like to thank several people who contributed to this update. These include Tim Brunner of IBM, Wolfgang Henke of Infineon, Margaret Conkling of Nikon Precision, Nigel Farrar, Vladmir Fleurov, Palash Das and Charles Hindes of Cymer, Andreas Erdmann of Fraunhofer-Institut für Integrierte Schaltungen, Doug Resnick and John Algair of Motorola, Wilhelm Maurer of Mentor Graphics, Christian Wagner and Robert Socha of ASML, Paul Graeupner of Carl Zeiss, Johannes Nieder of Leica, John Ricardi and Harry Rieger of JMAR, Ray Morgan of Canon, USA, Walter Gibson of XOS, and Sandy Burgan of DNS. Merry Schnell and Sharon Streams of the publications staff of SPIE have been very helpful and supportive. I apologize if I have failed to mention anyone who has helped me with this update. It has also been a privilege and joy to work on a more frequent basis with some exceptionally outstanding lithographers in my own department, as well as other lithography departments, at AMD. In particular, this includes manufacturing organizations, where the principles discussed in this book have been put skillfully applied and expertly enhanced to produce high performance non-volatile memory and the world s most powerful Windows-compatible microprocessors. From AMD, I would like to thank Bruno La Fontaine, Jongwook Kye, Ivan Lalovic, Adam Pawloski, Uzodinma Okoroanyanwu, Rolf Seltmann, Wolfram Grundke, and Rick Edwards for useful and informative discussions on lithography. I would like to thank my wife, Dr. Laurie Lauchlan, and my daughters, Sam and Sarah, who continued to exhibit amazing patience while I worked on the second edition of this book. On September 11, 2001, the world witnessed the destructive power of the irrational mind. I hope that this book will be a small reminder of the tremendous capacity of the rational human mind to improve the world around us.

18 6 CHAPTER 1 Each step of the lithographic process is discussed in this book. Pattern formation is of central importance because the great functionality of modern microelectronics has been enabled by the ability to pack large numbers of individual transistors in a unit area of silicon. The principles of optics relevant to imaging small features are covered in Chapter 2, while photoresists are discussed in Chapter 3. Methods of predicting lithographic performance are presented in Chapter 4. The primary tool used in lithography, the wafer stepper, is described in Chapter 5, and this leads into the topic of Chapter 6, overlay. Mask technology is the subject of Chapter 7. Advanced methods of optical lithography are reviewed in Chapter 8. The problem of measuring the small features created by the lithography process is addressed in Chapter 9. The limitations imposed by the laws of physics on optical methods are discussed in Chapter 10. Lithography costs are covered in Chapter 11. Finally, possible next-generation lithography options that might succeed optical lithography are reviewed in Chapter 12. Problems 1.1 For a mask that is 152 mm 152 mm, and assuming a 10-mm border at the edges of the plate is required to hold the mask, what is the largest field on the wafer that can be patterned if the lens reduction factor is 10, 5, and 4? 1.2 What are the nine principal steps in the lithographic process? Which steps are optional? 1.3 In the lithographic process, what are the materials called that are coated onto the wafers in order to capture the mask pattern?

62 50 CHAPTER F. Schellenberg, Resolution enhancement technology: the past, the present, and extensions for the future, Proceedings of SPIE 5377, pp (2004). 11. H.J. Levinson and W.H. Arnold, Focus: the critical parameter for submicron lithography, J. Vac. Sci. Technol. B 5, pp (1987). 12. W.H. Arnold and H.J. Levinson, Focus: the critical parameter for submicron lithography, part 2, Proceedings of SPIE 772, pp (1987). 13. L.Larmore, Introduction to Photographic Principles, Second edition, Dover Publications, New York (1965). 14. P.D. Blais, Edge acuity and resolution in positive type photoresist systems, Solid State Technol. 20, (1977). 15. W.H. Arnold and H.J. Levinson, High resolution optical lithography using an optimized single layer photoresist process, Proceedings of the Kodak Microelectronics Seminar, pp (1983). 16. Shipley Co., Newton, Mass., private communication. 17. Author, unpublished. 18. Nick Eib, private communication. 19. H.H. Hopkins, Wave Theory of Aberrations, Clarendon Press (1950). 20. L.E. Stillwagon, R.G. Larson, and G.N. Taylor, Planarization of substrate topography by spin coating, J. Electrochem. Soc. 134, (1991). 21. D.B. LaVergne and D.C. Hofer, Modeling planarization with polymers, Proceedings of SPIE 539, pp (1985). 22. L.K. White, Approximating spun-on, thin film planarization properties on complex topography, J. Electrochem. Soc. 132, pp (1985). 23. C. Nölscher, L. Mader, S. Guttenberger, and W. Arden, Search for the optimum numerical aperture, Microel. Eng. 11, pp (1990). 24. K. Yamanaka, H. Iwasaki, H. Nozue, and K. Kasama, NA and σ optimization for high-na I-line lithography, Proceedings of SPIE 1927, pp (1993). 25. W.N. Partlo, S.G. Olson, C. Sparkes, and J.E. Connors, Optimizing NA and sigma for sub-half-micrometer lithography, Proceedings of SPIE 1927, pp (1993). 26. B. Lin, The optimum numerical aperture for optical projection microlithography, Proceedings of SPIE 1463, pp , A. Suzuki, S. Yabu, and M. Ookubo, Intelligent optical system of a new stepper, Proceedings of SPIE 772, pp (1987). 28. H. Ohtsuka, K. Abe, Y. Itok and T. Taguchi, Quantitative evaluation method of conjugate point for practical evaluation of wafer stepper, Proceedings of SPIE 1088, pp (1989). 29. H. Fukuda, A. Imai, T. Terasawa, S. Okazaki, New approach to resolution limit and advanced image formation techniques in optical lithography, IEEE Trans. El. Dev. 38, No. 1, (1991). 30. J.W. Bossung, Projection printing characterization, Proceedings of SPIE 100, pp (1977).

198 188 CHAPTER A.R. Neureuther, P.K. Jain, and W.G. Oldham, Factors affecting linewidth control including multiple wavelength exposure and chromatic aberrations, Proceedings of SPIE 275, pp (1981). 15. I. Friedman, A. Offner, and H. Sewell, High resolution imagery: the matching of optical and resist systems, Proceedings of the KTI Microelectronics Seminar, pp, (1987). 16. W.H. Arnold, A. Minvielle, K. Phan, B. Singh and M. Templeton, 0.5 micron photolithography using high numerial aperture i-line wafer steppers, Proceedings of SPIE 1264, pp (1990). 17. T.C. Retzer and G. W. Gerung, New developments in short arc lamps, Illuminating Engineering 51, pp (1956). 18. W. E. Thouret, Tensile and thermal stresses in the envelope of high brightness high pressure discharge lamps, Illuminating Engineering 55, pp (1960). 19. G. Gear, Reliability and stability of mercury-arc lamps used in wafer steppers, Proceedings of Kodak Microelectronics Seminar, pp. 104 (1985). 20. D.W. Peters, Improvements in linesize control resulting from exposure lamp temperature stabilization and optimization, Proceedings of Kodak Microelectronics Seminar, pp (1986). 21. D. Cote, K. Andresen, D. Cronin, H. Harrold, M. Himel, J. Kane, J. Lyons, L. Markoya, C. Mason, D. McCafferty, M. McCarthy, G. O Connor, H. Sewell and D. Williamson, Micrascan III-performance of a third generation, catadioptric step-and-scan lithographic tool, Proceedings of SPIE 3051, pp (1997). 22. R. Sze, Rare-gas halide avalanche discharge lasers, IEEE J. Quantum Electron. QE-15, pp (1979). 23. H.J. Levinson, GCA ALS excimer stepper experience in the ASTC, Proceedings of Sematech DUV Lithography Workshop (1991). 24. Excimer Lasers, 2nd edition, Topics In Applied Physics, Vol. 30, ed. C. K. Rhodes, Springer Verlag, W. Partlo, R. Sandstrom, I. Fomenkov, and P. Das, A low cost of ownership KrF excimer laser using a novel pulse power and chamber configuration, Proceedings of SPIE 2440, pp (1995). 26. R. W. McCleary, P. J. Tompkins, M. D. Dunn, K. F. Walsh, J. F. Conway, and R. P. Mueller, Performance of a KrF excimer laser stepper, Proceedings of SPIE 922, pp (1988). 27. B. Rückle, P. Lokai, H. Rosenkranz, B. Kikolaus, H.J. Kahlert, B. Burghardt, D. Basting, and W. Mückenheim, Computerized wavelength stabilized nm excimer laser for stepper, Proceedings of SPIE 922, pp (1988). 28. R. Morton, I. Fomenkov, W. Partlo, P. Das, R. Sandstrom, Design considerations and performance of 1kHz KrF excimer lasers for DUV lithography, Proceedings of SPIE 2726, pp (1996). 041b061a72