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Sub-aperture EUV collector with dual-wavelength spectral purity filter

: Feigl, Torsten; Perske, Marco; Pauer, Hagen; Fiedler, Tobias; Zeitner, Uwe; Leitel, Robert; Eckstein, Hans Christoph; Schleicher, Philipp; Schröder, Sven; Trost, Marcus; Risse, Stefan; Steinkopf, Ralf; Scholze, F.; Laubis, C.


Wood, O.R. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Extreme Ultraviolet (EUV) Lithography VI : 23-26 February 2015, San Jose, California
Bellingham, WA: SPIE, 2015 (Proceedings of SPIE 9422)
ISBN: 9781628415247
Paper 94220E, 7 S.
Conference "Extreme Ultraviolet (EUV) Lithography" <6, 2015, San Jose/Calif.>
Fraunhofer IOF ()

The combination of a 10.6 μm main pulse CO2 laser and a 1064 nm pre-pulse Nd:YAG laser in EUV source concepts for HVM would require collector mirrors with an integrated spectral purity filter that suppresses both laser wavelengths. This paper discusses a new approach of a dual-wavelength spectral purity filter to suppress 10.6 μm and 1064 nm IR radiation at the same time. The dual-wavelength spectral purity filter combines two binary phase gratings that are optimized for 10.6 μm and 1064 nm, respectively. The dual phase grating structure has been realized on spherical sub-aperture EUV collector mirrors having an outer diameter of 150 mm. IR suppression factors of 260 at 10.6 μm and 620 at 1064 nm have been measured on the sub-aperture EUV collector while its EUV reflectance exceeded 64 % at 13.5 nm.