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High-temperature LPP collector mirror

: Feigl, T.; Yulin, S.; Benoit, N.; Kaiser, N.; Böwering, N.; Ershov, A.; Khodykin, O.; Viatella, J.; Bruzzone, K.; Fomenkov, I.; Myers, D.; Brandt, D.


Lercel, M.J. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Emerging Lithographic Technologies X. Vol.1 : 21-23 February 2006 San Jose, California, USA
Bellingham/Wash.: SPIE, 2006 (SPIE Proceedings Series 6151)
ISBN: 0-8194-6194-6
ISBN: 978-0-8194-6194-0
Conference "Emerging Lithographic Technologies" <10, 2006, San Jose/Calif.>
Conference Paper
Fraunhofer IOF ()
collector mirror; thermal stability; multilayer coating; optics lifetime

The EUV source output power and the collector optics lifetime have been identified as critical key issues for EUV lithography. In order to meet these requirements a heated collector concept was realized for the first time. An ellipsoidal collector Substrate with an outer diameter of 320 mm was coated with a laterally graded high-temperature multilayer. The interface-engineered Mo/Si multilayer coating was optimized in terms of high peak reflectivity at 13.5 nm and a working temperature of 400 °C. Barrier layers were introduced on both interfaces to block thermally induced interdiffusion processes of molybdenum and silicon to provide long-term optical stability of the multilayer at elevated temperatures. A normal-incidence reflectance of more than 40 % at 13.55 nm was measured after heating. After initial annealing at 400 °C for one hour, no degradation of the optical properties of these multilayer coatings occurred during both long-term heating tests for up to 100 hours and multiple annealing cycles. The successful realization of this high-temperature sub-aperture collector mirror represents a major step towards the implementation of the heated collector concept and illustrates the great potential of high-temperature EUV multilayer coatings.