Decomposition of catechol and carbonaceous residues on TiO2(110): A model system for cleaning of extreme ultraviolet lithography optics

P. Jacobson, S.-C. Li, C. Wang, U. Diebold

Department of Physics, Tulane University, New Orleans, Louisiana 70118, U.S.A.

J. Vac. Sci. Technol. B 26 (2008) 2236-2240

High energy photons used to expose photoresists in extreme ultraviolet lithography (92 eV, 13.5 nm) photoexcite electrons from Mo/Si multilayer mirror surfaces. Photoemitted electrons participate in the formation of carbonaceous residues on the mirror surface significantly affecting the mirror reflectivity. We explore mitigation strategies utilizing TiO2(110) as a model for the capping layer. Two carbon containing surfaces are examined; an ordered catechol monolayer and a carbonaceous layer. Excimer laser sources (XeF and KrF) coupled with oxidizing gas backgrounds (NO and O2) are shown to be effective for the photocatalytic removal of carbon. Utilizing x-ray photoemission spectroscopy and scanning tunneling microscopy carbon removal is shown to proceed through oxidation of the overlayer.

Reprints available from U. Diebold (diebold at iap_tuwien_ac_at).

Users with online access to Journal of Vacuum Science & Technology B can load the article from the publisher.