Share Email Print
cover

Proceedings Paper

Enhanced reflectivity and stability of high-temperature LPP collector mirrors
Format Member Price Non-Member Price
PDF $14.40 $18.00
cover GOOD NEWS! Your organization subscribes to the SPIE Digital Library. You may be able to download this paper for free. Check Access

Paper Abstract

The source output power and lifetime, including the collector optics lifetime, are among the key issues for EUV lithography systems. In order to meet the requirements for the EUV collector mirror, both the reflectivity and the long-term thermal stability of its multilayer coating have been enhanced considerably during recent development efforts. Sub-aperture ellipsoidal mirrors of different substrate materials with outer diameters of about 320 mm were coated with laterally graded high-temperature multilayers. The interface-engineered Mo/Si multilayer mirror (MLM) coatings were optimized in terms of high peak reflectivity at 13.5 nm and working temperatures above 400°C. Thin barrier layers were introduced on both interfaces to block thermally induced interdiffusion processes of molybdenum and silicon and to provide long-term optical stability of the coating at elevated temperatures. A normal-incidence reflectance of R ~ 60 % at 13.5 nm was measured on Si wafer samples after heating up to 600°C. No degradation of the optical properties of these multilayer coatings occurred during both long-term heating tests and multiple annealing cycles. On highly polished collector substrates with improved surface roughness a reflectance for s-polarized light exceeding peak values of R = 57 % was obtained. With optimized layer gradient the degree of wavelength matching was improved, as well, resulting in peak reflectivity values above 56 % throughout the clear aperture for a series of measurement points across the mirror. The corresponding area-weighted 2% in-band average reflectance for this collector mirror coating exceeds 52 % for unpolarized light.

Paper Details

Date Published: 3 September 2008
PDF: 8 pages
Proc. SPIE 7077, Advances in X-Ray/EUV Optics and Components III, 70771W (3 September 2008); doi: 10.1117/12.802322
Show Author Affiliations
Torsten Feigl, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Sergiy Yulin, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Marco Perske, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Hagen Pauer, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Mark Schürmann, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Norbert Kaiser, Fraunhofer-Institut für Angewandte Optik und Feinmechanik (Germany)
Norbert R. Böwering, Cymer, Inc. (United States)
Oleg V. Khodykin, Cymer, Inc. (United States)
Igor V. Fomenkov, Cymer, Inc. (United States)
David C. Brandt, Cymer, Inc. (United States)


Published in SPIE Proceedings Vol. 7077:
Advances in X-Ray/EUV Optics and Components III
Ali M. Khounsary; Christian Morawe; Shunji Goto, Editor(s)

© SPIE. Terms of Use
Back to Top