Surface-corrected multilayer-film mirrors with protected reflective surfaces, exposure systems comprising same, and associated methods

Abstract

Multilayer-film reflective mirrors are disclosed that exhibit desired optical characteristics and resistance to reflective-surface degradation. An exemplary multilayer-film mirror includes a base and a multilayer film on the base. The multilayer film is made of first and second layers alternatingly laminated at a prescribed period length. The surface of the multilayer film has an irregular surface profile, relative to the surface profile of the base. The multilayer film reflects incident extreme ultraviolet (EUV) light. A third layer, situated on and covering the surface of the multilayer film, is formed of a substance having substantially the same refractive index to EUV light as the refractive index of a vacuum. The third layer has a surface profile substantially the same as the surface contour of the base. The third layer is covered with a protective layer.