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

Yasuyuki Unno; Akiyoshi Suzuki

doi:10.1117/12.435667

14 September 2001 Analyses of imaging performance degradation caused by birefringence residual in lens materials

Yasuyuki Unno, Akiyoshi Suzuki

Proceedings Volume 4346, Optical Microlithography XIV; (2001) https://doi.org/10.1117/12.435667
Event: 26th Annual International Symposium on Microlithography, 2001, Santa Clara, CA, United States

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.

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Yasuyuki Unno and Akiyoshi Suzuki "Analyses of imaging performance degradation caused by birefringence residual in lens materials", Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); https://doi.org/10.1117/12.435667

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