Surface chemistry of Ru: Relevance to optics lifetime in EUVL

R. Wasielewski, B. V. Yakshinskiy, M. N. Hedhili, A. Ciszewski, T. E. Madey*

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

17 Scopus citations


Ruthenium capping layers ∼2 nm thick are used to protect and extend the lifetimes of Si/Mo multilayer mirrors used in extreme ultraviolet lithography (EUVL) applications. In the present work, we use ultrahigh vacuum surface science methods to address two aspects of Ru surface chemistry: (a) use of atomic hydrogen to remove oxygen from O-covered Ru, and (b) the effects of a model background hydrocarbon gas (methyl methacrylate, MMA) on the accumulation of carbon on a Ru(101̄0) single crystal surface. Atomic H is very effective in removing O from Ru even at 300K; the interpretation is that H reacts directly with adsorbed O to make OH, and a subsequent H atom reacts with OH to make H 2O, which desorbs at 300K. MMA adsorbs strongly on Ru in the first monolayer and dissociates upon heating; H 2 and CO desorption products are seen upon heating from 300 to 600K, while a fractional monolayer of C remains on the surface. Physisorbed multilayers of MMA form at temperatures below ∼170K. Thermal desorption of MMA dosed onto O-covered Ru shows that MMA reacts and completely removes an adsorbed O monolayer upon heating. Electron bombardment of MMA/Ru causes polymerization and also can induce accumulation of carbon - all depends on electron fluence, partial pressure of MMA, and substrate temperature.

Original languageEnglish (US)
Title of host publicationEMLC 2007
Subtitle of host publication23rd European Mask and Lithography Conference
StatePublished - 2007
Externally publishedYes
EventEMLC 2007: 23rd European Mask and Lithography Conference - Grenoble, France
Duration: Jan 22 2007Jan 25 2007

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherEMLC 2007: 23rd European Mask and Lithography Conference


  • Atomic H
  • EUV optics contamination
  • EUV optics lifetime
  • Electron induced reactions
  • Extreme ultraviolet lithography (EUVL)
  • Hydrogen
  • Methyl methacrylate (MMA)
  • Oxygen
  • Ru(101̄0)
  • Ruthenium

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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