Estimation of optimum density and temperature for maximum efficiency of 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-integra...

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Bibliographic Details
Published in:Journal of applied physics 2007-02, Vol.101 (3)
Main Authors: Masnavi, Majid, Nakajima, Mitsuo, Hotta, Eiki, Horioka, Kazuhiko, Niimi, Gohta, Sasaki, Akira
Format: Article
Language:English
Subjects:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
CHARGE STATES
ELECTRIC DISCHARGES
ELECTRON DENSITY
ELECTRON TEMPERATURE
EXTREME ULTRAVIOLET RADIATION
ION TEMPERATURE
LIGHT BULBS
PLASMA
PLASMA DENSITY
RADIANT HEAT TRANSFER
SPECTRA
TIN
TIN IONS
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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 Sn4+ to Sn13+ 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 ≃1018 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