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Proceedings Paper

Analyses of imaging performance degradation caused by birefringence residual in lens materials
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Paper Abstract

Influences of birefringence residual in lens materials of projection optics used for microlithography are investigated based on partially coherent imaging formula that has been modified to incorporate the change of polarization states in lens elements. Birefringent properties are represented by two- dimensional functions with respect to magnitude and fast-axis direction, and they are determined using random numbers to reproduce actual distributions in such materials as calcium fluoride. By repeating calculations using lens data created with different sets of random numbers, the degree of imaging performance degradation is analyzed statistically in terms of the magnitude of birefringence in each lens element, the number of lens element composing a projection lens, and the randomness of fast-axis distributions. It is found that the image contrast for a five-bar line/space pattern decreases squarely proportional to the magnitude, whereas the value decreases linearly proportional to the element number. The influence of randomness is understood in relation to image formations through random phase media.

Paper Details

Date Published: 14 September 2001
PDF: 12 pages
Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); doi: 10.1117/12.435667
Show Author Affiliations
Yasuyuki Unno, Canon Inc. (United States)
Akiyoshi Suzuki, Canon Inc. (Japan)

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

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