21 July 2000 Recent advances of three-aspherical-mirror system for EUVL
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A three-aspherical-mirror system for Extreme Ultraviolet Lithography has been developed. The aspherical mirrors were fabricated using the computer controlled optical surfacing (CCOS) process and a phase shift interferometer. The mirrors have a figure error of 0.58 nm and surface roughness of 0.3 nm. In order to obtain a high efficiency mirror, M1 and M2 were coated with a graded d-spacing Mo/Si multilayer and mirror M3 was coated with a uniform d-spacing Mo/Si multilayer. The peak reflectivity is 65% at the wavelength of 13.5 nm. The wavelength matching of each mirror spans 0.45 nm. The mirrors were aligned with a Fizeau-type phase shift interferometer, and a final wavefront error of less than 3 nm was achieved. Exposure experiments carried out at new Subaru synchrotron facility revealed that this system is capable of replicating a 56 nm pattern in a 10 mm X 1 mm exposure field.
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Hiroo Kinoshita, Hiroo Kinoshita, Takeo Watanabe, Takeo Watanabe, Yanqiu Li, Yanqiu Li, Atsushi Miyafuji, Atsushi Miyafuji, Tetsuya Oshino, Tetsuya Oshino, Katsumi Sugisaki, Katsumi Sugisaki, Katsuhiko Murakami, Katsuhiko Murakami, Shigeo Irie, Shigeo Irie, Shigeru Shirayone, Shigeru Shirayone, Shinji Okazaki, Shinji Okazaki, } "Recent advances of three-aspherical-mirror system for EUVL", Proc. SPIE 3997, Emerging Lithographic Technologies IV, (21 July 2000); doi: 10.1117/12.390091; https://doi.org/10.1117/12.390091

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