Long term tests of resonator optics in ArF excimer lasers

Nils Beermann; Holger Blaschke; Henrik Ehlers; Detlev Ristau; Dirk Wulff-Molder; Sigrid Jukresch; Ansgar Matern; Martin Bischoff; Dieter Gäbler; Norbert Kaiser

doi:10.1117/12.816706

21 April 2009 Long term tests of resonator optics in ArF excimer lasers

Nils Beermann, Holger Blaschke, Henrik Ehlers, Detlev Ristau, Dirk Wulff-Molder, Sigrid Jukresch, Ansgar Matern, Martin Bischoff, Dieter Gäbler, Norbert Kaiser

Author Affiliations +

Proceedings Volume 7131, XVII International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers; 713117 (2009) https://doi.org/10.1117/12.816706
Event: XVII International Symposium on Gas Flow and Chemical Lasers and High Power Lasers, 2008, Lisboa, Portugal

Abstract

The aim of this work is the optimization of the resonator optics of excimer laser systems to achieve longer lifetimes and to reduce the cost of ownership. The degradation after long-term exposure to high photon fluxes (typically 80 mJ/cm² at the ArF laser wavelength of 193 nm was analyzed. Based on the investigations, a model describing the process of the deterioration of the out-coupling partial reflector was developed. It was found that contamination of the optics by the laser's discharge electrodes leads to absorption losses on the surface facing the inside of the resonator. As a consequence, the laser irradiation causes a temperature gradient in the CaF₂-substrates which leads to crystal cleavage and braking of the optics. Defects on the outward surface are the origin for the growth of Calcite crystals and organic compounds by photo induced chemical reactions of the substrate material and contaminations in the purge gas. It was demonstrated that the lifetime of the resonator optics can be substantially increased by adapted optical designs and coatings.

Citation Download Citation

Nils Beermann, Holger Blaschke, Henrik Ehlers, Detlev Ristau, Dirk Wulff-Molder, Sigrid Jukresch, Ansgar Matern, Martin Bischoff, Dieter Gäbler, and Norbert Kaiser "Long term tests of resonator optics in ArF excimer lasers", Proc. SPIE 7131, XVII International Symposium on Gas Flow, Chemical Lasers, and High-Power Lasers, 713117 (21 April 2009); https://doi.org/10.1117/12.816706

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