21 March 2007 Long-term durability of a Ru capping layer for EUVL projection optics by introducing ethanol
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Abstract
The inhibition of contamination of Ru-capped Mo/Si multilayer mirrors was systematically investigated by introducing ethanol into a controlled vacuum that mainly consisted of water vapor. Water vapor was introduced up to several partial pressures of 1.0X10-7 to 3.8X10-5 Pa. At the lowest ethanol pressure, the same degree of reflectance degradation as in the water-only case was observed. However, reflectance degradation was suppressed at ethanol pressures higher than 2.0X10-6 Pa. In the condition of ethanol pressure of 2.0X10-6 Pa, the long-term durability of a Ru capping layer was investigated up to an EUV dose of 6000 J/mm2. This dose was corresponded to the 1-year use of a mirror which would be irradiated by the maximum power expected in actual EUVL tools. As a result of this investigation, it was found that reflectance degradation of a Ru capping layer was suppressed to less than 0.5% until 6000 J/mm2 by introducing ethanol.
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Yukinobu Kakutani, Masahito Niibe, Yoshio Gomei, Hiromitsu Takase, Shigeru Terashima, Shuichi Matsunari, Takashi Aoki, Yasuaki Fukuda, "Long-term durability of a Ru capping layer for EUVL projection optics by introducing ethanol", Proc. SPIE 6517, Emerging Lithographic Technologies XI, 651731 (21 March 2007); doi: 10.1117/12.711364; https://doi.org/10.1117/12.711364
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