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Study on the lifetime of Mo/Si multilayer optics with pulsed EUV-source at the ETS

: Schürmann, M.; Yulin, S.; Nesterenko, V.; Feigl, T.; Kaiser, N.; Tkachenko, B.; Schürmann, M.C.


Juha, L. ; Society of Photo-Optical Instrumentation Engineers -SPIE-, Bellingham/Wash.:
Damage to VUV, EUV, and X-ray Optics III : Prague, Czech Republic, April 2011
Bellingham, WA: SPIE, 2011 (Proceedings of SPIE 8077)
ISBN: 978-0-8194-8667-7
Paper 80770X
Conference "Damage to VUV, EUV, and X-Ray Optics" <3, 2011, Prague>
Fraunhofer IOF ()
EUVL; multilayer optic; optics lifetime; pulsed EUV source; in-situ cleaning

As EUV lithography is on its way into production stage, studies of optics contamination and cleaning under realistic conditions become more and more important. Due to this fact an Exposure Test Stand (ETS) has been constructed at XTREME technologies GmbH in collaboration with Fraunhofer IOF and with financial support of Intel Corporation. This test stand is equipped with a pulsed DPP source and allows for the simultaneous exposure of several samples. In the standard set-up four samples with an exposed area larger than 35 mm2 per sample can be exposed at a homogeneous intensity of 0.25 mW/mm2. A recent update of the ETS allows for simultaneous exposures of two samples with intensities up to 1.0 mW/mm2. The first application of this alternative set-up was a comparative study of carbon contamination rates induced by EUV radiation from the pulsed source with contamination rates induced by quasicontinuous synchrotron radiation. A modified gas-inlet system allows for the introduction of a second gas to the exposure chamber. This possibility was applied to investigate the efficiency of EUV-induced cleaning with different gas mixtures. In particular the enhancement of EUV-induced cleaning by addition of a second gas to the cleaning gas was studied.