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15 March 2016 The next-generation ArF excimer laser for multiple-patterning immersion lithography with helium free operation
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Multiple patterning ArF immersion lithography has been expected as the promising technology to satisfy tighter leading edge device requirements. A new ArF excimer laser, GT64A has been developed to cope with the prevention against rare resource shortage and the reduction of operational costs. GT64A provides the sophisticated technologies which realize the narrow spectral bandwidth with helium free operation. A helium gas purge has usually been employed due to the low refractive index variation with temperature rises within a line narrowing module(LNM). Helium is a non-renewable resource and the world’s reserves have been running out. Nitrogen gas with an affordable price has been used as an alternative purge gas of helium on the restrictive condition of low thermal loads. However, the refractive index variation of nitrogen gas is approximately ten times more sensitive to temperature rises than that of helium, and broadens a spectral bandwidth in the high duty cycle operations. The new LNM design enables heat effect in laser shooting at optical elements and mechanical components in the vicinity of an optical path to be lower. This reduces thermal wavefront deformation of a laser beam without helium gas purge within LNM, and narrows a spectrum bandwidth without helium purge. Gigaphoton proved that the new LNM enabled E95 bandwidth without control to improve a lot with nitrogen purge.
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Hirotaka Miyamoto, Takahito Kumazaki, Hiroaki Tsushima, Akihiko Kurosu, Takeshi Ohta, Takashi Matsunaga, and Hakaru Mizoguchi "The next-generation ArF excimer laser for multiple-patterning immersion lithography with helium free operation", Proc. SPIE 9780, Optical Microlithography XXIX, 97801I (15 March 2016);

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