Honing the accuracy of extreme-ultraviolet optical system testing: at-wavelength and visible-light measurements of the ETS Set-2 projection optic

Kenneth A. Goldberg; Patrick P. Naulleau; Jeffrey Bokor; Henry N. Chapman

doi:10.1117/12.472306

1 July 2002 Honing the accuracy of extreme-ultraviolet optical system testing: at-wavelength and visible-light measurements of the ETS Set-2 projection optic

Kenneth A. Goldberg, Patrick P. Naulleau, Jeffrey Bokor, Henry N. Chapman

Author Affiliations +

Proceedings Volume 4688, Emerging Lithographic Technologies VI; (2002) https://doi.org/10.1117/12.472306
Event: SPIE's 27th Annual International Symposium on Microlithography, 2002, Santa Clara, California, United States

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.

Citation Download Citation

Kenneth A. Goldberg, Patrick P. Naulleau, Jeffrey Bokor, and Henry N. Chapman "Honing the accuracy of extreme-ultraviolet optical system testing: at-wavelength and visible-light measurements of the ETS Set-2 projection optic", Proc. SPIE 4688, Emerging Lithographic Technologies VI, (1 July 2002); https://doi.org/10.1117/12.472306

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