Estimation of optimum density and temperature for maximum efficiencyof tin ions in Z discharge extreme ultraviolet sources

Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the narrow spectrum band of 13.5 ± 0.135 nm . A simplified collisional-radiative model and radiative transfer solution for an isotropic medium were utilized to investigate the wavelength-inte...

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Published in:Journal of applied physics 2007-02, Vol.101 (3), p.033306-033306-9
Main Authors: Masnavi, Majid, Nakajima, Mitsuo, Hotta, Eiki, Horioka, Kazuhiko, Niimi, Gohta, Sasaki, Akira
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Summary:Extreme ultraviolet (EUV) discharge-based lamps for EUV lithography need to generate extremely high power in the narrow spectrum band of 13.5 ± 0.135 nm . A simplified collisional-radiative model and radiative transfer solution for an isotropic medium were utilized to investigate the wavelength-integrated light outputs in tin (Sn) plasma. Detailed calculations using the Hebrew University-Lawrence Livermore atomic code were employed for determination of necessary atomic data of the Sn 4 + to Sn 13 + charge states. The result of model is compared with experimental spectra from a Sn-based discharge-produced plasma. The analysis reveals that considerably larger efficiency compared to the so-called efficiency of a black-body radiator is formed for the electron density ≃ 10 18 cm − 3 . For higher electron density, the spectral efficiency of Sn plasma reduces due to the saturation of resonance transitions.
ISSN:0021-8979
1089-7550
DOI:10.1063/1.2434987