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30 May 2003 Calcium fluoride for ArF laser lithography: characterization by in-situ transmission and LIF measurements
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An experimental setup was established for in situ transmission and laser induced fluorescence (LIF) measurements of CaF2 at 193 nm laser irradiation. The known rapid damage process in CaF2 upon ArF laser irradiation is shown to terminate for all tested samples within 3×104 laser pulses for the applied fluences. Furthermore, it is demonstrated that for typical application values the fluence dependent transmission (FDT) at the end of the rapid damage process is independent of the irradiation history and determined by the specific crystal quality. From the lifetimes and signal strengths of different present fluorescence bands the excitation and recording conditions for LIF investigations are derived. The results of laser induced fluorescence measurements at 193 nm excitation make evident that certain impurities or defects are responsible for the different transmission properties even of high purity CaF2 crystals. Comparing transmission and LIF data a quantitative correlation was found between selected emission bands and ArF laser stability of CaF2 material.
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Christian Muehlig, Wolfgang Triebel, Gabriela Toepfer, and A. Jordanov "Calcium fluoride for ArF laser lithography: characterization by in-situ transmission and LIF measurements", Proc. SPIE 4932, Laser-Induced Damage in Optical Materials: 2002 and 7th International Workshop on Laser Beam and Optics Characterization, (30 May 2003);

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