OPTICAL MEMBER FOR EUVL AND SURFACE TREATMENT METHOD THEREOF

摘要

The present invention is to provide an optical member for Extreme Ultra-Violet Lithography which is used for a reflective type mask, a mirror, etc. for EUVL and has excellent flatness and surface roughness on an optical surface thereof and in which chamfer parts are inhibited from being chipped. The present invention relates to a surface treatment method of an optical member for EUVL, including applying Gas Cluster Ion Beam etching using a source gas containing at least one of fluorine and chlorine to an optical surface of an optical member for EUVL, wherein the optical member is made of a silica glass material having an OH concentration of 100 ppm or more, containing TiO2 and containing SiO2 as a major component.