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Proceedings Paper

Carbon accumulation and mitigation processes, and secondary electron yields of ruthenium surfaces
Author(s): B. V. Yakshinskiy; R. Wasielewski; E. Loginova; Theodore E. Madey
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Paper Abstract

Metallic ruthenium capping layers ~2 nm thick protect and extend the lifetimes of Mo/Si multilayer mirrors used in extreme ultraviolet lithography (EUVL) applications. However, Ru-capped mirrors experience a loss of reflectivity after prolonged exposure to EUV radiation. In the present work, we use ultrahigh vacuum surface science methods to address several aspects of Ru surface chemistry that may impact on Ru capping layer stability and mitigation processes. (1) We characterize the composition and stability of Ru surfaces that simulate surfaces of Ru-capped multilayer mirrors, under exposure to different background gases (water, methyl methacrylate (MMA)) and to electron irradiation. Evidence for some mitigation of carbon accumulation during electron bombardment in MMA + water vapor is found. (2) We report the photon-energy dependence of secondary electron yield (SEY) measurements for clean Ru, O-dosed and C-dosed Ru, and Ru-capped multilayer mirrors using synchrotron radiation near 13.5 nm at Brookhaven National Synchrotron Light Source (NSLS). Much of the radiation-induced chemistry on the surfaces of capping layers is induced by low-energy secondary electrons rather than direct photoexcitation, so the SEY is an important parameter affecting mirror lifetimes in EUVL.

Paper Details

Date Published: 21 March 2007
PDF: 11 pages
Proc. SPIE 6517, Emerging Lithographic Technologies XI, 65172Z (21 March 2007); doi: 10.1117/12.711785
Show Author Affiliations
B. V. Yakshinskiy, Rutgers, The State Univ. of New Jersey (United States)
R. Wasielewski, Rutgers, The State Univ. of New Jersey (United States)
E. Loginova, Rutgers, The State Univ. of New Jersey (United States)
Theodore E. Madey, Rutgers, The State Univ. of New Jersey (United States)

Published in SPIE Proceedings Vol. 6517:
Emerging Lithographic Technologies XI
Michael J. Lercel, Editor(s)

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