Plasma-assisted oxide removal from ruthenium-coated EUV optics

A. Dolgov, C.J. Lee, F. Bijkerk, A. Abrikosov, V.M. Krivtsun, D. Lopaev, O. Yakushev, M. van Kampen

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Abstract

An experimental study of oxide reduction at the surface of ruthenium layers on top of multilayer mirrors and thin Ru/Si films is presented. Oxidation and reduction processes were observed under conditions close to those relevant for extreme ultraviolet lithography. The oxidized ruthenium surface was exposed to a low-temperature hydrogen plasma, similar to the plasma induced by extreme ultraviolet radiation. The experiments show that hydrogen ions are the main reducing agent. Furthermore, the addition of hydrogen radicals increases the reduction rate beyond that expected from simple flux calculations. We show that low-temperature hydrogen plasmas can be effective for reducing oxidized top surfaces. Our proof-of-concept experiments show that an in situ, EUV-generated plasma cleaning technology is feasible.

Original languageEnglish
Article number153301
Number of pages9
JournalJournal of Applied Physics
Volume123
Issue number15
DOIs
Publication statusPublished - 18 Apr 2018

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    Dolgov, A., Lee, C. J., Bijkerk, F., Abrikosov, A., Krivtsun, V. M., Lopaev, D., ... van Kampen, M. (2018). Plasma-assisted oxide removal from ruthenium-coated EUV optics. Journal of Applied Physics, 123(15), [153301]. https://doi.org/10.1063/1.5006771