Articles you may be interested inEffect of interface treatment with assisted ion beam on Mo-Si multilayer formation for mask blanks for extreme ultraviolet lithographyCleaning of extreme ultraviolet lithography optics and masks using 13.5 nm and 172 nm radiation Influence of glass substrate surface roughness on extreme ultraviolet reflectivity of Mo ∕ Si multilayer To protect the surface oxidation of Mo/ Si multilayer films by extreme ultraviolet ͑EUV͒ irradiation under a vacuum atmosphere with residual water, two experiments were carried out. One consisted of examining the oxidation protection effect for isopropyl alcohol ͑IPA͒ and n-decane gases. The reflectivity change of the Ru-capped multilayer film by EUV irradiation was investigated under a vacuum atmosphere with residual water vapor at a pressure of 1.3ϫ 10 −5 Pa, and, in addition, each hydrocarbon ͑HC͒ gas was introduced by changing its pressure. A protective effect against oxidation was observed in both gases when introduced at a pressure in the order of 10 −6 Pa. For IPA, no remarkable decrease in the reflectivity was observed even when the introductory pressure was raised to the order of 10 −4 Pa. However, for n-decane, the reflectivity decreased remarkably when pressure in the order of 10 −5 Pa was introduced. The other experiment consisted of examining the reduction effect of the oxidized surface by EUV irradiation when introducing HC gas. Ru-and Si-capped multilayers were once oxidized by EUV irradiation under a water vapor atmosphere. However, for the Ru-capped multilayer, the reflectivity was recovered when EUV was irradiated in the presence of ethanol gas at a pressure of 3.8ϫ 10 −5 Pa. The oxide layer of the Ru cap was reduced at this time.