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Proceedings Paper

Liquid immersion lithography at 157 nm
Author(s): Takuya Hagiwara; Toshiyuki Ishimaru; Shou Tsuji; Kiyoshi Fujii; Yasuo Itakura; Osamu Wakabayashi; Youichi Kawasa; Keiji Egawa; Ikuo Uchino; Akira Sumitani; Yusuke Saito; Kazuhiko Maeda
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Paper Abstract

We performed an initial evaluation of 157-nm immersion lithography. The 157-nm immersion fluid needs to have both a high refractive index and high transmittance at a wavelength of 157 nm. This paper focuses on the transparency of the fluid. We evaluated the transparency of straight-chain perfluoroalkane and perfluoroether using a semi-empirical molecular orbital method. We found that perfluoroether has lower absorption at 157 nm than perfluoroalkane, and increasing the amount of ether bonds in perfluoroether can further reduce the absorption. Moreover, we found that designing the molecular structure with ether bonds so that the number of successive CFx is balanced should further improve transparency. Although the commercial perfluoropolyether BARRIERTA® J25V contains a trifluoromethyl group in one of its side-chains, it satisfied the above conditions and achieved high transmittance of 1.0 cm-1 at 157 nm. The sensitivity characteristics of the XP2332C and F-SSQ resists were evaluated by dry and immersion exposure using BARRIERTA® J25V immersion fluid, and no noticeable changes were seen in the development contrast for either exposure condition for either of these two resists. To perform 157-nm immersion exposures, we constructed a Michelson interferometric exposure tool, which let us create an interference pattern with sufficient optical contrast. We obtained a resolution of 60-nm line-and-space pattern having a good rectangular shape by immersion exposure using this interferometric exposure tool, F-SSQ resist, and BARRIERTA® J25V immersion fluid without using a top-coat.

Paper Details

Date Published: 12 May 2005
PDF: 12 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.599379
Show Author Affiliations
Takuya Hagiwara, Semiconductor Leading Edge Technologies, Inc. (Japan)
Toshiyuki Ishimaru, Semiconductor Leading Edge Technologies, Inc. (Japan)
Shou Tsuji, Semiconductor Leading Edge Technologies, Inc. (Japan)
Kiyoshi Fujii, Semiconductor Leading Edge Technologies, Inc. (Japan)
Yasuo Itakura, Komatsu Ltd. (Japan)
Osamu Wakabayashi, Komatsu Ltd. (Japan)
Youichi Kawasa, Komatsu Ltd. (Japan)
Keiji Egawa, Komatsu Ltd. (Japan)
Ikuo Uchino, Komatsu Ltd. (Japan)
Akira Sumitani, Komatsu Ltd. (Japan)
Yusuke Saito, Central Glass Co., Ltd. (Japan)
Kazuhiko Maeda, Central Glass Co., Ltd. (Japan)

Published in SPIE Proceedings Vol. 5754:
Optical Microlithography XVIII
Bruce W. Smith, Editor(s)

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