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Proceedings Paper

Smoothing of diamond-turned substrates for extreme-ultraviolet lithography illuminators
Author(s): Regina Soufli; Eberhard Spiller; Mark A. Schmidt; Jeffrey C. Robinson; Sherry L. Baker; Susan Ratti; Michael A. Johnson; Eric M. Gullikson
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Paper Abstract

Condenser optics in extreme ultraviolet lithography (EUVL) systems are subjected to frequent replacement as they are positioned close to the illumination source, where increased heating and contamination occur. In the case of aspherical condenser elements made by optical figuring/finishing, their replacement can be very expensive (several hundred thousand dollars). One approach to this problem would be to manufacture inexpensive illuminator optics that meet all required specifications and could be replaced at no substantial cost. Diamond-turned metal substrates are a factor of 100 less expensive than conventional aspherical substrates but have insufficient finish, leading to unacceptably low EUV reflectance after multilayer coating. In this work it is shown that, by applying a smoothing film prior to multilayer coating, the high spatial frequency roughness of a diamond-turned metal substrate is reduced from 1.76 to 0.27 nm rms while the figure slope error is maintained at acceptable levels. Metrology tests performed at various stages of the fabrication of the element demonstrated that it satisfied all critical figure and finish specifications as illuminator. Initial experimental results on the stability and performance of the optic under a real EUVL plasma source environment show no accelerated degradation when compared to conventional substrates.

Paper Details

Date Published: 13 January 2004
PDF: 7 pages
Proc. SPIE 5193, Advances in Mirror Technology for X-Ray, EUV Lithography, Laser, and Other Applications, (13 January 2004); doi: 10.1117/12.509220
Show Author Affiliations
Regina Soufli, Lawrence Livermore National Lab. (United States)
Eberhard Spiller, Lawrence Livermore National Lab. (United States)
Lawrence Livermore National Lab. (United States)
Mark A. Schmidt, Lawrence Livermore National Lab. (United States)
Jeffrey C. Robinson, Lawrence Livermore National Lab. (United States)
Sherry L. Baker, Lawrence Livermore National Lab. (United States)
Susan Ratti, Lawrence Livermore National Lab. (United States)
Michael A. Johnson, Lawrence Livermore National Lab. (United States)
Eric M. Gullikson, Lawrence Berkeley National Lab. (United States)


Published in SPIE Proceedings Vol. 5193:
Advances in Mirror Technology for X-Ray, EUV Lithography, Laser, and Other Applications
Ali M. Khounsary; Udo Dinger; Kazuya Ota, Editor(s)

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