28 May 2004 Verification of compaction and rarefaction models for fused silica with 40 billion pulses of 193-nm excimer laser exposure and their effects on projection lens imaging performance
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Proceedings Volume 5377, Optical Microlithography XVII; (2004); doi: 10.1117/12.537132
Event: Microlithography 2004, 2004, Santa Clara, California, United States
Abstract
Extensive testing of fused silica has been completed over the past few years by several researchers. A generalized model has been proposed that describes both the compaction that occurs at high peak intensities and the rarefaction that occurs at lower peak intensities. An exposure setup has been constructed to help verify these damage models and to determine the fitting parameters for various types and processing of fused silica. This setup simultaneously exposes samples to two sets of intensities, each set with a different integrated-square pulse width. To make these tests relevant to the microlithography community, the energy densities chosen for these tests span the range found in the projection optics of a 193nm excimer laser-based microlithography tool (50μj/cm2 - 400μj/cm2 ). The samples have been exposed for 40 billion pulses with wavefront measurements made periodically with both 633nm interferometry and 193mn interferometry. This large number of pulses represents the equivalent of several years worth of lens exposure. Data for several fused silica samples will be presented and comparisons will be made to the proposed damage model. According to the obtained parameters, optical performance will be estimated during long term laser exposure on the projection optics. We take into consideration actual light intensity on each lens element for several illumination conditions. We will discuss the difference of the impact on optical performance between different fused silica materials, illumination conditions, reticle transmission, pulse durations, number of pulses, and so on.
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J. Martin Algots, Richard Sandstrom, William Partlo, Kazuhiro Takahashi, Hiroyuki Ishii, Yasuo Hasegawa, "Verification of compaction and rarefaction models for fused silica with 40 billion pulses of 193-nm excimer laser exposure and their effects on projection lens imaging performance", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004); doi: 10.1117/12.537132; https://doi.org/10.1117/12.537132
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KEYWORDS
Silica

Data modeling

Wavefronts

Wavefront aberrations

Refractive index

Reticles

Statistical modeling

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