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30 September 2011 Roughness characterization of large EUV mirror optics by laser light scattering
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Optical components for extreme ultraviolet (EUV) lithography at a wavelength of 13.5 nm face tremendous requirements on the surface finish, because large amounts of the EUV light are lost as a result of roughness-induced scattering. In this paper we present a novel approach for the roughness characterization of large EUV mirror optics based on light scattering measurements at a wavelength of 442 nm. The high sensitivity to roughness and the robustness of this method are exemplified for a 660 mm diameter collector mirror substrate. Area covering images of the high-spatial frequency roughness are retrieved which enable a detailed prediction of the EUV reflectance prior to coating. The results are compared to EUV reflectance measurements after coating.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Marcus Trost, Sven Schröder, Torsten Feigl, Angela Duparré, and Andreas Tünnermann "Roughness characterization of large EUV mirror optics by laser light scattering", Proc. SPIE 8169, Optical Fabrication, Testing, and Metrology IV, 81690P (30 September 2011);

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