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Title: Conversion efficiency of extreme ultraviolet radiation in laser-produced plasmas

Abstract

A simple analytical model is presented for the conversion of laser beam energy into extreme ultraviolet radiation. The model is compared with experimental results to show good agreements under different conditions of the laser wavelength {lambda}{sub L}, the laser intensity S{sub L}, the pulse duration t{sub L}, and the target atomic number Z{sub 0}. It turns out that relatively high conversion efficiencies are obtained when the Planck optical thickness of the plasma is {tau}{approx_equal}0.3-0.5, which is attained under an optimized combination of S{sub L} and t{sub L} once {lambda}{sub L} is fixed. The {lambda}{sub L} scaling on the conversion efficiency is derived.

Authors:
; ; ; ; ; ;  [1];  [2]
  1. Institute of Laser Engineering, Osaka University, Yamada-oka 2-6, Osaka 565-0871 (Japan)
  2. (Japan)
Publication Date:
OSTI Identifier:
20782572
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 13; Journal Issue: 3; Other Information: DOI: 10.1063/1.2187445; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ATOMIC NUMBER; CONVERSION; EFFICIENCY; EXTREME ULTRAVIOLET RADIATION; LASER RADIATION; LASER-PRODUCED PLASMA; LASERS; LIGHT TRANSMISSION; PULSES; WAVELENGTHS

Citation Formats

Murakami, M., Fujioka, S., Nishimura, H., Ando, T., Ueda, N., Shimada, Y., Yamaura, M., and Institute for Laser Technology, Yamada-oka 2-6, Osaka 565-0871. Conversion efficiency of extreme ultraviolet radiation in laser-produced plasmas. United States: N. p., 2006. Web. doi:10.1063/1.2187445.
Murakami, M., Fujioka, S., Nishimura, H., Ando, T., Ueda, N., Shimada, Y., Yamaura, M., & Institute for Laser Technology, Yamada-oka 2-6, Osaka 565-0871. Conversion efficiency of extreme ultraviolet radiation in laser-produced plasmas. United States. doi:10.1063/1.2187445.
Murakami, M., Fujioka, S., Nishimura, H., Ando, T., Ueda, N., Shimada, Y., Yamaura, M., and Institute for Laser Technology, Yamada-oka 2-6, Osaka 565-0871. Wed . "Conversion efficiency of extreme ultraviolet radiation in laser-produced plasmas". United States. doi:10.1063/1.2187445.
@article{osti_20782572,
title = {Conversion efficiency of extreme ultraviolet radiation in laser-produced plasmas},
author = {Murakami, M. and Fujioka, S. and Nishimura, H. and Ando, T. and Ueda, N. and Shimada, Y. and Yamaura, M. and Institute for Laser Technology, Yamada-oka 2-6, Osaka 565-0871},
abstractNote = {A simple analytical model is presented for the conversion of laser beam energy into extreme ultraviolet radiation. The model is compared with experimental results to show good agreements under different conditions of the laser wavelength {lambda}{sub L}, the laser intensity S{sub L}, the pulse duration t{sub L}, and the target atomic number Z{sub 0}. It turns out that relatively high conversion efficiencies are obtained when the Planck optical thickness of the plasma is {tau}{approx_equal}0.3-0.5, which is attained under an optimized combination of S{sub L} and t{sub L} once {lambda}{sub L} is fixed. The {lambda}{sub L} scaling on the conversion efficiency is derived.},
doi = {10.1063/1.2187445},
journal = {Physics of Plasmas},
number = 3,
volume = 13,
place = {United States},
year = {Wed Mar 15 00:00:00 EST 2006},
month = {Wed Mar 15 00:00:00 EST 2006}
}
  • We have investigated the spot size effects on the extreme ultraviolet conversion efficiency (CE) of CO{sub 2} laser-produced Sn plasmas. The estimated CE of the laser to 13.5 nm radiation, within a 2% bandwidth, using a 10.6 {mu}m CO{sub 2} laser with various pulse widths (25-55 ns) showed a double hump structure during a target-lens scan, where the CE is nearly 25% lower at the best focal position. Density analysis of the CO{sub 2} laser-produced plasma showed steep density gradients at the best focal position, and a reduction in CE at the best focal position, which is explained by themore » lack of efficient coupling between the laser and the plasma.« less
  • The conversion efficiency of spectral emission from laser-irradiated solid targets was investigated for short wavelength source development. The plasma brightness was quantified using absolutely calibrated detectors for 20 materials and spectra were obtained between 50 and 200 A. Laser parameters such as wavelength, pulse length, intensity, and spot size were systematically varied to establish a comprehensive database for source optimization. Qualitative differences in the underlying dominant emission features as a function of atomic number and laser wavelength were observed that accounted for the relatively high spectral conversion efficiencies produced. In the specific case of Sn, a conversion efficiency greater thanmore » 0.8{percent}/eV has been observed in the technologically important region of {lambda}=134.0 A using a laser intensity of 1{endash}2{times}10{sup 11} W/cm{sup 2}.« less
  • Opacity effects on extreme ultraviolet (EUV) emission from laser-produced tin (Sn) plasma have been experimentally investigated. An absorption spectrum of a uniform Sn plasma generated by thermal x rays has been measured in the EUV range (9-19 nm wavelength) for the first time. Experimental results indicate that control of the optical depth of the laser-produced Sn plasma is essential for obtaining high conversion to 13.5 nm-wavelength EUV radiation; 1.8% of the conversion efficiency was attained with the use of 2.2 ns laser pulses.
  • The direct comparison of the emission characteristics of an extreme ultraviolet (EUV) light between the CO{sub 2} and the Nd:YAG laser-produced plasmas (LPP) with a solid tin target is reported. In the case of the Nd:YAG LPP, the conversion efficiency (C.E.) peaked at a laser intensity of about 5x10{sup 10} W/cm{sup 2} and decreased at higher laser intensity. In the case of the CO{sub 2} LPP, the C.E. monotonically increased up to 2x10{sup 10} W/cm{sup 2}, where the C.E. is comparable to the maximum C.E. of the Nd:YAG LPP. The spectral efficiency of the Nd:YAG LPP within the 2% bandwidthmore » around 13.5 nm decreased with laser intensity. The corresponding spectral efficiency of the CO{sub 2} LPP was almost constant. This observation indicates the potential of the CO{sub 2} laser-produced LPP as the EUV light source for the EUV lithographic systems.« less
  • Out-of-band (OOB) radiation (at wavelengths longer than 130 nm) from an extreme ultraviolet (EUV) light source reduces the precision of lithography. The energy of the OOB radiation from laser-produced Sn plasmas were measured by using an absolutely calibrated transmission grating spectrometer equipped with a charge-coupled device. The dependence of the OOB radiant energy on the mass and size of the tin fuel was clarified. The dominant source of the OOB radiation is peripheral heating around the laser spot via electron thermal conduction and radiation from the high-temperature EUV emission region.