A novel photo-thermal setup for determination of absorptance losses and wavefront deformations in DUV optics

K. Mann; A. Bayer; U. Leinhos; T. Miege; B. Schäfer

doi:10.1117/12.775453

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7 March 2008 A novel photo-thermal setup for determination of absorptance losses and wavefront deformations in DUV optics

K. Mann, A. Bayer, U. Leinhos, T. Miege, B. Schäfer

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Proceedings Volume 6924, Optical Microlithography XXI; 69242P (2008) https://doi.org/10.1117/12.775453
Event: SPIE Advanced Lithography, 2008, San Jose, California, United States

Abstract

Lens heating due to absorbed UV laser radiation can diminish the achievable spatial resolution of the lithographic process in semiconductor wafer steppers. At the Laser- Laboratorium Göttingen a measurement system for quantitative registration of this thermal lens effect was developed. It is based upon a strongly improved Hartmann-Shack wavefront sensor with extreme sensitivity, accomplishing precise online monitoring of wavefront deformations of a collimated test laser beam transmitted through the laser-irradiated site of a sample. Caused by the temperature-dependent refractive index as well as thermal expansion, the formerly plane wavefront of the test laser is distorted to form a rotationally symmetric valley, being equivalent to a convex lens. The observed wavefront distortion is a quantitative measure of the absorption losses in the sample. Thermal theory affords absolute calibration of absorption coefficients.

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K. Mann, A. Bayer, U. Leinhos, T. Miege, and B. Schäfer "A novel photo-thermal setup for determination of absorptance losses and wavefront deformations in DUV optics", Proc. SPIE 6924, Optical Microlithography XXI, 69242P (7 March 2008); https://doi.org/10.1117/12.775453

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