18 October 2004 Fabrication of aspherical mirrors for EUV projection optics set-3 of HiNA
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We developed a high-numerical-aperture EUV exposure tool (HiNA). HiNA is equipped with an illumination system, projection optics, a mask stage and a wafer stage in the vacuum chamber. The projection optics consist of two aspherical mirrors (M1 and M2). The numerical aperture of the optics is 0.3. Thus far, we fabricated two sets of projection optics (set-1 and set-2). The wavefront errors of set-1 and set-2 were 7.5nm rms and 1.9nm rms, respectively. We developed the third set of projection optics (set-3), the target wavefront error of which was less than 1nm rms. In set-3, we also attempted to reduce flare. We completed the mirror polishing, coating and mirror adjustment of set-3. Using a new polishing method, we successfully reduced low-spatial-frequency roughness (LSFR), mid-spatial-frequency roughness (MSFR) and high-spatial-frequency roughness (HSFR) simultaneously. The predicted wavefront error calculated from the LSFR number was 0.69nm rms. MSFR, which strongly affects the flare of the optics, was significantly reduced to less than 0.2nm rms. The estimated flare was 7%, which is significantly reduced to one-fourth that of set-2. The wavefront error of set-3 was measured with the visible-light point diffraction interferometer (PDI) after coating and assembly. The wavefront error measured after adjustment and cramping of the adjustment system was 0.90nm rms, which is less than one-half the wavefront error of set-2.
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Tetsuya Oshino, Tetsuya Oshino, Shin-ichi Takahashi, Shin-ichi Takahashi, Takahiro Yamamoto, Takahiro Yamamoto, Tatsuro Miyoshi, Tatsuro Miyoshi, Masayuki Shiraishi, Masayuki Shiraishi, Takaharu Komiya, Takaharu Komiya, Noriaki Kandaka, Noriaki Kandaka, Hiroyuki Kondo, Hiroyuki Kondo, Kiyoto Mashima, Kiyoto Mashima, Kazushi Nomura, Kazushi Nomura, Katsuhiko Murakami, Katsuhiko Murakami, Hiroaki Oizumi, Hiroaki Oizumi, Iwao Nishiyama, Iwao Nishiyama, Shinji Okazaki, Shinji Okazaki, } "Fabrication of aspherical mirrors for EUV projection optics set-3 of HiNA", Proc. SPIE 5533, Advances in Mirror Technology for X-Ray, EUV Lithography, Laser, and Other Applications II, (18 October 2004); doi: 10.1117/12.559210; https://doi.org/10.1117/12.559210


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