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Title: Tuning extreme ultraviolet emission for optimum coupling with multilayer mirrors for future lithography through control of ionic charge states

We report on the identification of the optimum plasma conditions for a laser-produced plasma source for efficient coupling with multilayer mirrors at 6.x nm for beyond extreme ultraviolet lithography. A small shift to lower energies of the peak emission for Nd:YAG laser-produced gadolinium plasmas was observed with increasing laser power density. Charge-defined emission spectra were observed in electron beam ion trap (EBIT) studies and the charge states responsible identified by use of the flexible atomic code (FAC). The EBIT spectra displayed a larger systematic shift of the peak wavelength of intense emission at 6.x nm to longer wavelengths with increasing ionic charge. This combination of spectra enabled the key ion stage to be confirmed as Gd{sup 18+}, over a range of laser power densities, with contributions from Gd{sup 17+} and Gd{sup 19+} responsible for the slight shift to longer wavelengths in the laser-plasma spectra. The FAC calculation also identified the origin of observed out-of-band emission and the charge states responsible.
Authors:
; ; ;  [1] ; ; ;  [2] ; ; ;  [3] ; ;  [4] ;  [5]
  1. Department of Advanced Interdisciplinary Sciences, Center for Optical Research and Education (CORE), Utsunomiya University, Yoto 7-1-2, Utsunomiya, Tochigi 321-8585 (Japan)
  2. School of Physics, University College Dublin, Belfield, Dublin 4 (Ireland)
  3. Institute for Laser Science, The University of Electro-Communications, Chofu, Tokyo 182-8585 (Japan)
  4. Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki 305-8573 (Japan)
  5. Department of Electrical Engineering, Nagaoka University of Technology, Kami-tomiokamachi 1603-1, Nagaoka, Niigata 940-2188 (Japan)
Publication Date:
OSTI Identifier:
22275740
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Applied Physics; Journal Volume: 115; Journal Issue: 3; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; 74 ATOMIC AND MOLECULAR PHYSICS; CHARGE STATES; ELECTRON BEAMS; EMISSION SPECTRA; EXTREME ULTRAVIOLET RADIATION; GADOLINIUM IONS; LASER-PRODUCED PLASMA; LAYERS; MIRRORS; MULTICHARGED IONS; NEODYMIUM LASERS; PHOTON EMISSION; POWER DENSITY