Abstract

High-efficiency, normal-incidence X-ray multilayer mirrors are now being used for a variety of practical applications. Among these is Extreme Ultraviolet (EUV) lithography. A practical EUV lithography printing tool may include as many as seven normal-incidence multilayer reflections, so it is imperative that the mirror substrates be fabricated with low surface roughness in order to achieve high reflectance, and consequently high system throughput (wafers/hour.) In order to develop the necessary techniques to fabricate such mirrors, it is first necessary to accurately quantify the surface finish requirements of the mirror substrates, and to then identify the surface finish metrology tools that can be used by the manufacturer during the substrate fabrication process. To this end, we have examined correlations between direct surface finish measurement techniques and normal-incidence, soft X-ray reflectance measurements of highly-polished X-ray multilayer mirrors.

© 1994 Optical Society of America