EUV Sources for Lithography

Excerpt

Until recently, EUV source power was the number one challenge to implementing EUV lithography (EUVL) in the high-volume manufacturing of computer chips. But due to the dedicated efforts of a few dozen research groups around the world, EUV source technology continues to advance. Today, with tremendous improvements in source power and other characteristics, source power is no longer the leading challenge. EUV sources have evolved from a laboratory concept to reality, with alpha-level EUV sources being delivered for integration in alpha-level EUV scanners.

This reference book contains 38 chapters contributed by leading researchers and suppliers in the field of EUV sources for EUVL. The chapter topics are intended to cover the needs of practitioners of the technology as well as readers who want an introduction to EUV sources. The book begins with in-depth coverage of EUV source requirements and the status of the technology, followed by a review of fundamental atomic data and descriptions of theoretical models of discharge-produced plasma (DPP) and laser-produced plasma (LPP) based EUV sources, prominent DPP and LPP designs, and alternative technologies for producing EUV radiation. Also covered are topics in EUV source metrology, EUV source components (collectors, electrodes), debris mitigation, and mechanisms of component erosion in EUV sources.

As EUV source technology has progressed, researchers and commercial suppliers around the world have published more than 100 papers per year, and the amount of technical data on EUV source technology continues to increase. My effort as volume editor has been to produce an authoritative reference book on EUV source technology, which has not existed until now. In the future one may need to consult the proceedings of SEMATECH's EUV Source Workshops and SPIE's Microlithography conference for the most recent performance improvements in EUV sources, but this text will still deliver the in-depth technical background information on particular technical approaches and on EUV source technology in general.

The primary strength of this book is that the contributions came from leading experts. The choice of having many authors per section has produced a comprehensive and true reference book, covering a range of technical options and opinions. I have done my best to make each chapter a complete reference in itself, though some sections—usually the introductory sections of chapters—inevitably overlap. For example, although each chapter mentions the requirements for a source, the reader is encouraged to consult Chapter 2 to understand the details of EUV source requirements. Likewise, many authors refer to certain issues such as debris generation in their chapters; however, the reader is directed to Chapter 37 for a comprehensive reading on the fundamentals of debris generation and mitigation.

This project has been successful due to the dedication and hard work of many technologists worldwide. Therefore, I would like to acknowledge and thank the authors who have worked very hard to produce a reference chapter on their technical work. Their quality manuscripts made my job as an editor much easier. This book is essentially the fruit of their labor.

I would like to thank my colleagues at SEMATECH's member companies, as well as the authors in this volume who took the time to review the chapters by their colleagues. I would especially like to thank some of the referees who reviewed multiple chapters: Vadim Banine, Vladimir Borisov, Peter Choi, Akira Endo, Igor Fomenkov, Samir Ellwi, Björn Hansson, Ahmed Hassanein, Lennie Klebanoff, Konstantin Koshelev, Thomas Krücken, Hans J. Kunze, Rainer Lebert, Malcolm McGeoch, Katsunobu Nishihara, Gerry O'Sullivan, Joseph Pankert, Martin Richardson, David Ruzic, Uwe Stamm, Yusuke Teramoto, and Sergey Zakharov.

I would also like to acknowledge the contributions of my family, whose influence, encouragement, and support have allowed me to undertake such a project. First of all, my father, Mr. Om Prakash Bakshi, MA, set a very high standard for written communication and the pursuit of excellence, which still today I can only strive to meet. My mother, Mrs. Pushpa Bakshi, MA, retired lecturer of the Punjabi language, always set the example of hard work and taught me a pragmatic approach toward solving everyday problems, which still guides me. My wife, Laura Coyle, encouraged me to undertake this intellectual pursuit and has always been an example of innovation and uncompromising attention to quality and detail for achieving perfection, as evident in her own achievements. Laura's and my daughter Emily's encouragement have allowed me to continue and complete this project. For these reasons, I have dedicated this book to my parents and my wife and daughter.

I would like to thank SPIE acquisitions editor Timothy Lamkins, with whom I worked to generate the concept of this book. I would also like to thank SPIE editor Margaret Thayer, who made one of the largest book projects ever undertaken by SPIE Press a very smooth process. I very much appreciate her support and hard work for making this book project a reality.

Finally, I would like to thank my former manager, Kevin Kemp, for his guidance and support in this project, and my employer, SEMATECH, which exemplifies industry cooperation in the semiconductor community. SEMATECH has created a global platform to facilitate consensus on the direction of technology and to promote cooperative work in the pre-competitive arena of computer chip manufacturing. Hopefully, this book will set an example of how a large number of experts and competitors can cooperate to produce a reference work to benefit an entire industry.

Vivek Bakshi

December 2005