Liquid immersion lithography at 157 nm

Takuya Hagiwara; Toshiyuki Ishimaru; Shou Tsuji; Kiyoshi Fujii; Yasuo Itakura; Osamu Wakabayashi; Youichi Kawasa; Keiji Egawa; Ikuo Uchino; Akira Sumitani; Yusuke Saito; Kazuhiko Maeda

doi:10.1117/12.599379

12 May 2005 Liquid immersion lithography at 157 nm

Takuya Hagiwara, Toshiyuki Ishimaru, Shou Tsuji, Kiyoshi Fujii, Yasuo Itakura, Osamu Wakabayashi, Youichi Kawasa, Keiji Egawa, Ikuo Uchino, Akira Sumitani, Yusuke Saito, Kazuhiko Maeda

Author Affiliations +

Proceedings Volume 5754, Optical Microlithography XVIII; (2005) https://doi.org/10.1117/12.599379
Event: Microlithography 2005, 2005, San Jose, California, United States

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 CF_x 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.

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Takuya Hagiwara, Toshiyuki Ishimaru, Shou Tsuji, Kiyoshi Fujii, Yasuo Itakura, Osamu Wakabayashi, Youichi Kawasa, Keiji Egawa, Ikuo Uchino, Akira Sumitani, Yusuke Saito, and Kazuhiko Maeda "Liquid immersion lithography at 157 nm", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); https://doi.org/10.1117/12.599379

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