12 April 2001 Two-photon equivalent weighting of spatial excimer laser beam profiles
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Abstract
Damage in optical materials for semiconductor lithography applications caused by exposure to 248 or 193 nm light is usually two-photon driven, hence it is a nonlinear function of incident intensity. Materials should be tested with flat- topped temporal and spatial laser beam profiles to facilitate interpretation of data, but in reality this is hard to achieve. Sandstrom provided a formula that approximates any given temporal pulse shape with a two- photon equivalent rectangular pulse (Second Symposium on 193 nm Lithography, Colorado Springs 1997). Known as the integral-square pulse duration, this definition has been embraced as an industry standard. Originally faced with the problem of comparing results obtained with pseudo-Gaussian spatial profiles to literature data, we found that a general solution for arbitrarily inhomogeneous spatial beam profiles exists which results in a definition much similar to Sandstrom's. In addition, we proved the validity of our approach in experiments with intentionally altered beam profiles.
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Eric Eva, Eric Eva, Harry H. Bauer, Harry H. Bauer, K. Metzger, K. Metzger, A. Pfeiffer, A. Pfeiffer, } "Two-photon equivalent weighting of spatial excimer laser beam profiles", Proc. SPIE 4347, Laser-Induced Damage in Optical Materials: 2000, (12 April 2001); doi: 10.1117/12.425074; https://doi.org/10.1117/12.425074
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