20 December 2001 Prevention of MoSi multilayer reflection loss in EUVL tools
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Abstract
Extreme ultraviolet lithography requires vacuum conditions in the optical train. In order to maintain sufficient energy throughput, reflection reduction of multilayer mirrors due to contamination has to be minimized. We report on oxidation and carbonization experiments on MoSi mirrors under exposure with EUV radiation from a synchrotron. To mimic the effects of EUV radiation we also exposed samples using an electron gun. The oxidation rate was found to be ~0.015 nm/h per mW/mm2 of EUV radiation under vacuum conditions that are typical for a high throughput EUVL system, I.e. 10-6 mbar H2O. This oxidation can to a large extend be suppressed by using smart gas blend strategies during exposure, e.g. using ethanol. A deposition rate of 0.25 nm/h was found when the hydrocarbon pressure of Fomblin was reduced to 10(superscript -9 mbar. We demonstrate that carbonization can be suppressed by admitting oxygen during electron gun exposure.
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Hans Meiling, Hans Meiling, Bas Mertens, Bas Mertens, Frank Stietz, Frank Stietz, Marco Wedowski, Marco Wedowski, Roman Klein, Roman Klein, Ralph Kurt, Ralph Kurt, Eric Louis, Eric Louis, Andrey E. Yakshin, Andrey E. Yakshin, } "Prevention of MoSi multilayer reflection loss in EUVL tools", Proc. SPIE 4506, Soft X-Ray and EUV Imaging Systems II, (20 December 2001); doi: 10.1117/12.450949; https://doi.org/10.1117/12.450949
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