Optical member, method of manufacturing the same, and projection exposure system

摘要

A method of manufacturing an optical member includes a crystal growing step and a carving step. The crystal growing step includes melting a mixture of fluoride powder and a scavenger at a melting temperature of a melting point for the fluoride and above, and then crystallizing the melted fluid and further cooling down an obtained fluoride crystal in a temperature range from 1000° C. to 900° C. by a temperature decreasing rate in a range from 0.1 to 5° C./hr. The carving step includes carving an optical member out of the fluoride crystal obtained in the crystal growing step such that the optical member is made of a fluoride crystal in which a maximum diameter d_max of scattering bodies existing internally and a quantity n_s of the scattering bodies per 1 cm³ satisfy a condition represented by the following formula (1): 0max²xn_s<6.5x10^-4 (cm^-1) (1).