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Proceedings Paper

Laser-induced birefringence in fused silica from polarized lasers
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Paper Abstract

Fused silica, when exposed to excimer laser light, exhibits permanent anisotropic birefringence and wavefront changes. These laser-induced changes depend on the silica composition and processing conditions. The optical anisotropy is most clearly observed in samples that are exposed with linear polarization. This polarization-induced effect has been known for several years, but has become much more important with the advent of immersion lithography and its associated very high numerical apertures. High numerical aperture optics require controlled polarization, notably linear polarization, in order to maintain phase contrast at the image. When birefringence and wavefront changes are induced by laser exposure, the image contrast at the wafer deteriorates. We interpret the changes in optical properties in terms of permanent anisotropic strain induced by laser damage, and the associated strain-induced optical effects. This is accomplished using the mathematics of tensors to account for anisotropic strain and optical anisotropy, and using finite element analysis to calculate the strain fields taking the sample and exposure geometries into account. We report the relations between underlying density and strain anisotropy changes and the induced birefringence and wavefront for a given experimental sample geometry. We also report some examples of the different degree of laser damage from silica with different compositions and processing conditions.

Paper Details

Date Published: 12 May 2005
PDF: 8 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.598741
Show Author Affiliations
Ulrich Neukirch, Corning Inc. (United States)
Douglas C. Allan, Corning Inc. (United States)
Nicholas F. Borrelli, Corning Inc. (United States)
Christine E. Heckle, Corning Inc. (United States)
Michal Mlejnek, Corning Inc. (United States)
Johannes Moll, Corning Inc. (United States)
Charlene M. Smith, Corning Inc. (United States)

Published in SPIE Proceedings Vol. 5754:
Optical Microlithography XVIII
Bruce W. Smith, Editor(s)

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