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Proceedings Paper

Spectral measurement of ultra line-narrowed F2 laser
Author(s): Osamu Wakabayashi; Jun Sakuma; Toru Suzuki; Hirokazu Kubo; Naoki Kitatochi; Takashi Suganuma; Takanori Nakaike; Takahito Kumazaki; Kazuaki Hotta; Hakaru Mizoguchi; Kiyoharu Nakao; Tadashi Togashi; Yasuo Nabekawa; Shuntaro Watanabe
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Paper Abstract

F2 lasers are the light source of choice for microlithographic tools enabling structures below the 70 nm technology node. Accurate measurements of the spectrum of F2 lasers are therefore very important. We have succeeded in measuring the spectrum of an ultra line narrowed F2 laser using a VUV grating spectrometer calibrated with a 153 nm coherent light source (153CLS). As a first step in the development of a 157 nm coherent light source (157CLS), the less complex 153CLS has been built. Using resonant two-photon processes and four-wave mixing in Xe, this method provided a tunable laser system with high conversion efficiency and a very narrow linewidth, which can be approximated by a (delta) function. The 153CLS included a pulsed, single-mode tunable Ti:sapphire laser (768.0 nm), a third harmonic generation unit (256.0 nm) and an Xe gas cell. The 153CLS had a linewidth of 0.007pm (FWHM) and a power of 0.05mW at 1000 Hz. The VUV grating spectrometer and a Michelson interferometer for F2 lasers have also been developed. The instrument function of the spectrometer has been measured with the 153CLS. Experimental and theoretical instrument functions were in good agreement (FWHM: 0.30pm). The instrument function at 157 nm was therefore estimated to have the theoretical FWHM of 0.31 pm. The spectral linewidth of the line-selected F2 laser has been measured under various laser conditions with the spectrometer as well as with the interferometer. Results show good agreement between both measurements. The spectrum of the ultra line narrowed F2 laser was measured with the VUV grating spectrometer calibrated using the 153CLS. The laser's FWHM of the deconvolved spectrum was 0.29pm. The deconvolved spectral purity containing 95% of the total laser energy is less than 0.84pm.

Paper Details

Date Published: 14 September 2001
PDF: 8 pages
Proc. SPIE 4346, Optical Microlithography XIV, (14 September 2001); doi: 10.1117/12.435638
Show Author Affiliations
Osamu Wakabayashi, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Jun Sakuma, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Toru Suzuki, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Hirokazu Kubo, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Naoki Kitatochi, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Takashi Suganuma, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Takanori Nakaike, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Takahito Kumazaki, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Kazuaki Hotta, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Hakaru Mizoguchi, ASET-Association of Super-Advanced Electronics Technologies (Japan)
Kiyoharu Nakao, Association of Super-Advanced Electronics Technologies (Japan)
Tadashi Togashi, Univ. of Tokyo (Japan)
Yasuo Nabekawa, Univ. of Tokyo (Japan)
Shuntaro Watanabe, Univ. of Tokyo (Japan)


Published in SPIE Proceedings Vol. 4346:
Optical Microlithography XIV
Christopher J. Progler, Editor(s)

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