Molecular contamination mitigation in EUVL by environmental control

Norbert Koster*, Bas Mertens, Rik Jansen, Annemieke Van De Runstraat, Frank Stietz, Marco Wedowski, Hans Meiling, Roman Klein, Alexander Gottwald, Frank Scholze, Matthieu Visser, Ralph Kurt, Peer Zalm, Eric Louis, Andrey Yakshin

*Corresponding author for this work

Research output: Contribution to journalConference articleAcademicpeer-review

36 Citations (Scopus)


EUVL tools operate under vacuum conditions to avoid absorption losses. Under these conditions, the MoSi multilayer mirrors are contaminated, resulting in reduced reflection and thus throughput. We report on experiments on MoSi mirrors exposed to EUV radiation from a synchrotron. To mimic the effects of EUV radiation we also exposed samples using an electron gun. The oxidation rate was found to be ∼0.016 nm/h per mW/mm2 of EUV radiation under conditions expected for a high throughput EUVL system. This oxidation can to a large extent be suppressed by using smart gas blend strategies during exposure, e.g. using ethanol. A carbon growth rate of 0.25 nm/h was found for a hydrocarbon pressure of 10-9 mbar Fomblin. We demonstrate that carbonisation can be suppressed by admitting oxygen during electron gun exposure.

Original languageEnglish
Pages (from-to)65-76
Number of pages12
JournalMicroelectronic engineering
Publication statusPublished - 1 Jul 2002
Externally publishedYes
EventMicro and Nano Engineering, MNE 2001 - Grenoble, France
Duration: 16 Sep 200119 Sep 2001


  • Carbon growth
  • Contamination
  • EUVL
  • Mirror lifetime
  • MoSi mirrors
  • Oxidation
  • Reflection loss


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