Advanced Processes for 193-nm Immersion Lithography

Excerpt

The benefits of using liquids in optical microscopes were first demonstrated in the 1880s. A century later, in the 1980s, experiments with immersion technology demonstrated its potential for use in modern lithography. In 2002, when 157-nm lithography was delayed by a host of technical problems, the development of 193-nm immersion lithography for use in fabricating integrated circuits gained momentum. The development of 193-nm immersion lithography (193i) occurred much faster than did any previous lithographic technology. Currently, 193i is widely used to manufacture advanced microelectronic devices at the 45-nm node. The entire transition from proof of concept to delivery of a mass production tool took only about four years.

This rapid growth was possible because of the combined efforts of all sectors of the lithography community, including the manufacturers of scanners, materials, and integrated circuits. Much of the research critical to the rapid advancement of 193i has been published in the last few years in various journals and proceedings. One of the goals of this book is to summarize this information so that those new to the field as well as current practitioners may increase their understanding of this important technology.

Thus, while actively involved in evaluating new materials, equipment, and processes for 193i imaging, Yayi Wei began writing the manuscript for this book. During the summer of 2008, Robert Brainard, a researcher developing new resist materials, joined Yayi as his coauthor to help prepare the manuscript. Their collaboration resulted in this timely monograph that presents the knowledge critical for establishing high-yield cost-effective 193i processes and materials. The text can be used as course material for graduate students of electrical engineering, material sciences, physics, chemistry, and microelectronics engineering. It can also be used to train engineers involved in the manufacture of integrated circuits.

A large portion of this book is concerned with the challenges and opportunities of water-based 193-nm immersion lithography. The first chapter provides a broad overview of 193i lithography. The second chapter describes the track where most of the processes occur. The book continues with descriptions of the interactions between the immersion fluid (water) and the resist in terms of contact angle, leaching of resist components, and topcoats. It also provides a comprehensive summary of various immersion-related defects and defect-reduction strategies. It covers topics that were originally developed in “dry” lithography and are extendable to immersion 193-nm lithography, discussing strategies for antireflection control, shrink processes, trim processes, double exposure, double patterning, and line-edge roughness. The book concludes with a chapter describing research efforts aimed at further extensions of immersion lithography to higher numerical aperture (NA) and resolution through the development of high-index lithography. Discussion of some topics (e.g., optical theory of hyper-NA) was kept brief when well described in other monographs.

The knowledge of 193i is still growing and will continue to mature as it is used more frequently in mass production. We appreciate any suggestions from our readers on how to update this material. Your input will help us improve subsequent editions of this book.

Yayi Wei

Altamont, New York

Robert L. Brainard

College of Nanoscale Science and Engineering University at Albany, State University of New York

January 2009