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Proceedings Paper

Optimum mask and source patterns to print a given shape
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Paper Abstract

New degrees of freedom can be optimized in mask shapes when the source is also adjustable, because required image symmetries can be provided by the source rather than the collected wavefront. The optimized mask will often consist of novel sets of shapes that are quite different in layout from the target IC patterns. This implies that the optimization algorithm should have good global convergence properties, since the target patterns may not be a suitable starting solution. We have developed an algorithm that can optimize mask and source without using a starting design. Examples are shown where the process window obtained is between 2 and 6 times larger than that achieved with standard RET methods. The optimized masks require phase shift, but no trim mask is used. Thus far we have only optimized 2D patterns over small fields (periodicities of approximately 1 micrometer or less). We also discuss mask optimization with fixed source, source optimization with fixed mask, and the re-targeting of designs in different mask regions to provide a common exposure level.

Paper Details

Date Published: 14 September 2001
PDF: 17 pages
Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); doi: 10.1117/12.435748
Show Author Affiliations
Alan E. Rosenbluth, IBM Thomas J. Watson Research Ctr. (United States)
Scott J. Bukofsky, IBM Semiconductor Research and Development Ctr. (United States)
Michael S. Hibbs, IBM Microelectronics Div. (United States)
Kafai Lai, IBM Semiconductor Research and Development Ctr. (United States)
Antoinette F. Molless, IBM Semiconductor Research and Development Ctr. (United States)
Rama Nand Singh, IBM Thomas J. Watson Research Ctr. (United States)
Alfred K. K. Wong, IBM Semiconductor Research and Development Ctr. (Hong Kong)


Published in SPIE Proceedings Vol. 4346:
Optical Microlithography XIV
Christopher J. Progler, Editor(s)

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