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Proceedings Paper

Phase-shifting mask topography effects on lithographic image quality
Author(s): Christophe Pierrat; Alfred K. K. Wong; Sheila Vaidya; Matthew Vernon
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Paper Abstract

The impact of phase-shifting mask topography on wafer exposure was studied via simulations and experimentation using phase-shifting masks fabricated by etching the quartz to define the shifted areas. The influence of the refractive index of the chromium layer was shown to be minimal and for all the simulations, the refractive index was assumed to be 2.5 - 2.0 j at 248 nm. As the chromium profiles marginally influence the linewidth of the resist patterns, the simulated intensity assumes vertical profiles. Moreover, it was shown experimentally and using simulations that the quartz profiles have a large impact on the wafer results. For vertical quartz profiles, the intensity of the light going through the etched portion of the mask is lower than that going through the unetched portion of the mask and varies with feature size. The consequences are that 0 degree(s) and 180 degree(s) phases cannot be interchanged blindly during the layout of a phase-shifting mask and that the pinhole phase-defect repair technique consisting in etching 360 degree(s) phase slots in the quartz will not yield the same intensity profile as a defect- free region. These problems can be addressed either by optimizing the quartz profiles or by biasing the size of the features depending on the type of pattern.

Paper Details

Date Published: 8 August 1993
PDF: 14 pages
Proc. SPIE 1927, Optical/Laser Microlithography, (8 August 1993); doi: 10.1117/12.150446
Show Author Affiliations
Christophe Pierrat, AT&T Bell Labs. (United States)
Alfred K. K. Wong, Univ. of California/Berkeley (United States)
Sheila Vaidya, AT&T Bell Labs. (United States)
Matthew Vernon, Photronics (United States)

Published in SPIE Proceedings Vol. 1927:
Optical/Laser Microlithography
John D. Cuthbert, Editor(s)

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