Theoretical discussion on reduced aberration sensitivity of enhanced alternating phase-shifting masks

Alfred K. K. Wong

doi:10.1117/12.474585

30 July 2002 Theoretical discussion on reduced aberration sensitivity of enhanced alternating phase-shifting masks

Alfred K. K. Wong

Proceedings Volume 4691, Optical Microlithography XV; (2002) https://doi.org/10.1117/12.474585
Event: SPIE's 27th Annual International Symposium on Microlithography, 2002, Santa Clara, California, United States

Abstract

Two theories are developed to quantify image skew of photomask features caused by aberrations. In one formulation, the extent of image distortion can be described by the image asymmetry, which captures both image shift and sidelobe intensity imbalance. This quantity is equivalent to the shift of the image centroid. In situations where one is more concerned with placement error than centroid shift, the change in the location of the intensity extremum can be expressed as functions of the mask spectrum and the wave aberration. This theory on image shift is applied to the study of enhanced alternating PSMs. Although the optimal mask pattern is aberration-function-specific, mask spectra with gradual variations have lower placement sensitivity in general. These theories are applicable to all mask technologies and patterns.

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Alfred K. K. Wong "Theoretical discussion on reduced aberration sensitivity of enhanced alternating phase-shifting masks", Proc. SPIE 4691, Optical Microlithography XV, (30 July 2002); https://doi.org/10.1117/12.474585

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