Patent ID: 8243364
Filing Date: 2012-08-14
Classification: B82Y,G02B,G03F,G21K

Abstract:
1. A reflective optical element for the extreme ultraviolet (EUV) and soft X-ray wavelength regions, the reflective optical element comprising a multilayer system and a protective layer system, wherein: the protective layer system comprises at least two layers; the protective layer system terminates at a vacuum side in least one layer of a material with a refractive index whose real part at an operating wavelength between 12.5 nm and 15 nm is between 0.90 and 1.03, and whose imaginary part at an operating wavelength between 12.5 nm and 15 nm is between 0 and 0.025; and a first layer of the at least two layers of the protective layer system comprises one or more materials selected from the group consisting of SiO