@inproceedings{fd92fcc693c84ae380ce97b80a21a02a,
title = "Surface chemistry of Ru: Relevance to optics lifetime in EUVL",
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{\=1}0) 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.",
keywords = "Atomic H, EUV optics contamination, EUV optics lifetime, Electron induced reactions, Extreme ultraviolet lithography (EUVL), Hydrogen, Methyl methacrylate (MMA), Oxygen, Ru(10{\=1}0), Ruthenium",
author = "R. Wasielewski and Yakshinskiy, {B. V.} and Hedhili, {Mohamed Nejib} and A. Ciszewski and Madey, {T. E.}",
year = "2007",
month = nov,
day = "5",
doi = "10.1117/12.737185",
language = "English (US)",
isbn = "0819466557",
series = "Proceedings of SPIE - The International Society for Optical Engineering",
booktitle = "EMLC 2007",
note = "EMLC 2007: 23rd European Mask and Lithography Conference ; Conference date: 22-01-2007 Through 25-01-2007",
}