Prevention of MoSi multilayer reflection loss in EUVL tools

Hans Meiling; Bas Mertens; Frank Stietz; Marco Wedowski; Roman Klein; Ralph Kurt; Eric Louis; Andrey E. Yakshin

doi:10.1117/12.450949

20 December 2001 Prevention of MoSi multilayer reflection loss in EUVL tools

Hans Meiling, Bas Mertens, Frank Stietz, Marco Wedowski, Roman Klein, Ralph Kurt, Eric Louis, Andrey E. Yakshin

Proceedings Volume 4506, Soft X-Ray and EUV Imaging Systems II; (2001) https://doi.org/10.1117/12.450949
Event: International Symposium on Optical Science and Technology, 2001, San Diego, CA, United States

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.

Citation Download Citation

Hans Meiling, Bas Mertens, Frank Stietz, Marco Wedowski, Roman Klein, Ralph Kurt, Eric Louis, and 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); https://doi.org/10.1117/12.450949

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