Surface chemistry of Ru: relevance to optics lifetime in EUVL

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

doi:10.1117/12.737185

3 May 2007 Surface chemistry of Ru: relevance to optics lifetime in EUVL

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

Proceedings Volume 6533, 23rd European Mask and Lithography Conference; 653316 (2007) https://doi.org/10.1117/12.737185
Event: European Mask and Lithography Conference2007, 2007, Grenoble, France

Abstract

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(10 1010) 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 H₂O, which desorbs at 300K. MMA adsorbs strongly on Ru in the first monolayer and dissociates upon heating; H2 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.

Citation Download Citation

R. Wasielewski, B. V. Yakshinskiy, M. N. Hedhili, A. Ciszewski, and T. E. Madey "Surface chemistry of Ru: relevance to optics lifetime in EUVL", Proc. SPIE 6533, 23rd European Mask and Lithography Conference, 653316 (3 May 2007); https://doi.org/10.1117/12.737185

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