Secondary electron yield measurements of carbon covered multilayer optics

Juequan Chen, Eric Louis, Jan Verhoeven, Rob Harmsen, Christopher James Lee, Monika Lubomska, Maarten van Kampen, Willem van Schaik, Frederik Bijkerk

Research output: Contribution to journalArticleAcademicpeer-review

13 Citations (Scopus)

Abstract

Carbon contamination on extreme ultraviolet (EUV) optics has been observed in EUV lithography. In this paper, we performed in situ monitoring of the build-up and removal of carbon contamination on Mo/Si EUV multilayers by measuring the secondary electron yield as a function of primary electron energy. An electron beam with an energy of 2 keV was used to simulate the EUV radiation induced carbon contamination. For a clean EUV multilayer, the maximum secondary electron yield is about 1.5 electrons per primary electron at a primary electron energy of 467 eV. The maximum yield reduced to about 1.05 at a primary electron energy of 322 eV when the surface was covered by a non-uniform carbon layer with a maximum thickness of 7.7 nm. By analyzing the change in the maximum secondary electron yield with the final carbon layer thickness, the limit of detection was estimated to be less than 0.1 nm.
Original languageEnglish
Pages (from-to)354-361
Number of pages8
JournalApplied surface science
Volume257
Issue number2
DOIs
Publication statusPublished - 2010

Keywords

  • IR-75235
  • METIS-270287

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