28 May 2004 Excimer-laser-induced defect generation in Lithosil
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Fused silica is used as lens material in DUV microlithography systems. The exposure of fused silica to high-energy excimer laser pulses over long periods of time modifies the material. Marathon experiments were conducted at different energy densities with the KrF- and ArF excimer laser to describe the material parameters under long time irradiation. A model was developed to describe the radiation induced absorption and the change of the index of refraction. The defect generation is associated with the consumption of hydrogen. The dependence of hydrogen consumption on the wavelength of irradiation, the energy density and the initial hydrogen content was investigated in detail. The saturation of H2 consumption in Lithosil was proved by different experiments. The results are in very good agreement with the model calculations.
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Ute Natura, Oliver Sohr, Martin Letz, Rolf Martin, Michael Kahlke, Gabriele Fasold, "Excimer-laser-induced defect generation in Lithosil", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004); doi: 10.1117/12.531653; https://doi.org/10.1117/12.531653

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