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Revisiting a Conference and Some Ongoing Problems
May 9, 2008
During a conversation on some of the lithography and metrology technology problems that our industry faces as we continue racing after Moore’s and Wang’s Laws, my friend Alain Diebold, Empire Professor of Nanoscale Science at the University of Albany’s College of Nanoscale Science and Engineering, had some thoughts on the recent 2007 ITRS Metrology and Lithography Roadmaps, which I think are on point and would like to share with you.
“The Roadmaps discussed process and measurement challenges associated with new lithography processes such as dual patterning (See “EUV Research Helps Solve 193 nm Resist Problems,” SI March 2008),” he said. “A bird’s eye view of a set of similar processes such as dual patterning, spacer patterning, and double exposure shows that they are all at different stages of development for future technology nodes. Many of the 2008 SPIE Advanced Lithography conference papers covered some recent advances in these processes.
Required litho CD uniformity as a function of the technology node. Source: ASML.
“While evidence from previous SPIE meetings indicates that spacer patterning is already used in manufacturing, one of the most challenging aspects of these processes is that there are two sets of linewidths and lineshapes making the etch step even more complicated; lineshape control tolerances are becoming even more critical. Among the many interesting papers was one by NIST and Intel’s Kwang-Woo Choi, et al. titled, ‘Characterization of the Latent Image to Developed Image in Model EUV Photoresists.’ He made the point here that measuring the latent image is extremely difficult, and the use of AFM to measure topographical changes from exposure deserved mention.
Required litho CD uniformity as function of the technology node. Source: ASML.
“AFM probe tip shape and use of calibration standards and deconvolution of tip shape from sample shape has been the topic of papers by NIST’s John Villarrubia in past SPIE Advanced Lithography conferences. One aspect of the measurement of latent image for double exposure processes involves potentially making the measurement between exposures inside the exposure tool itself. Meeting the measurement needs of advanced lithography processes is going to require near-term advances, meaning that the advances must be made using existing measurement systems. The magnitude of the challenge is evidenced by ASM Lithography’s Chief Scientist Bill Arnold’s SPIE paper, ‘Towards 3-nm Overlay and Critical Dimension Uniformity: An Integrated Error Budget for Double Patterning Lithography,’ in which he discussed 3-nm overlay and CD uniformity requirements.”
All of which seems well-worth reviewing.
Posted by Alexander E. Braun on May 9, 2008 | Comments (0)
