Molybdenum-ruthenium/beryllium multilayer coatings

A newly developed beryllium-based multilayer system consisting of polycryst alline Be and amorphous MoRu layers is presented. The multilayer exhibits m any remarkable properties: reflectivity as high as 69.3% at a wavelength of 11.4 nm (achieved with 50 bilayers giving a bandwidth of 0.35 nm), near-ze ro intrinsic stress, and excellent smoothing properties. As compared with M o/Si multilayers at 13.4 nm, the shorter wavelength of 11.4 nm is better ma tched to the spectral output of gas-jet laser produced plasma sources, allo wing a much higher optical throughput of the extreme ultraviolet lithograph y (EUVL) tool. The properties of MoRu/Be are compared to other beryllium-ba sed multilayers, which have been considered for reflective coatings for EUV L optics. (C) 2000 American Vacuum Society. [S0734-2101(00)08402-5].