Development of Extreme Ultra-Violet Lithography System
Hiroo KINOSHITA, Takeo WATANABE, Kazuhiro HAMAMOTO and Harushige TSUBAKINO
Abstract: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 figure errors 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 M3 was coated with a uniform d-spacing Mo/Si multilayer. The peak reflectivity was 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 2nm was achieved. Using this system, exposure experiments were performed. 60 nm L&S pattern‚“ on the exposure area of 10mm x 10mm were achieved. Key Words:EUVL, Lithography, Multilayer, Reflection mask, Resist, Mirror optics, SR, Laser plasma source