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Proceedings Paper

Honing the accuracy of extreme-ultraviolet optical system testing: at-wavelength and visible-light measurements of the ETS Set-2 projection optic
Author(s): Kenneth A. Goldberg; Patrick P. Naulleau; Jeffrey Bokor; Henry N. Chapman
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Paper Abstract

As the quality of optical systems for extreme ultraviolet lithography improves, high-accuracy wavefront metrology for alignment and qualification becomes ever more important. To enable the development of diffraction-limited EUV projection optics, visible-light and EUV interferometries must work in close collaboration. We present a detailed comparison of EUV and visible-light wavefront measurements performed across the field of view of a lithographic-quality EUV projection optical system designed for use in the Engineering Test Stand developed by the Virtual National Laboratory and the EUV Limited Liability Company. The comparisons reveal that the present level of RMS agreement lies in the 0.3-0.4-nm range. Astigmatism is the most significant aberration component for the alignment of this optical system; it is also the dominant term in the discrepancy, and the aberration with the highest measurement uncertainty. With EUV optical systems requiring total wavefront quality in the (lambda) EUV/50 range, and even higher surface-figure quality for the individual mirror elements, improved accuracy through future comparisons, and additional studies, are required.

Paper Details

Date Published: 1 July 2002
PDF: 9 pages
Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); doi: 10.1117/12.472306
Show Author Affiliations
Kenneth A. Goldberg, Lawrence Berkeley National Lab. (United States)
Patrick P. Naulleau, Lawrence Berkeley National Lab. (United States)
Jeffrey Bokor, Lawrence Berkeley National Lab. and Univ. of California/Berkeley (United States)
Henry N. Chapman, Lawrence Livermore National Lab. (United States)

Published in SPIE Proceedings Vol. 4688:
Emerging Lithographic Technologies VI
Roxann L. Engelstad, Editor(s)

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