METHOD FOR PRODUCING CALCIUM FLUORIDE SINGLE CRYSTAL AND CALCIUM FLUORIDE SINGLE CRYSTAL

摘要

PROBLEM TO BE SOLVED: To solve the problem that it is difficult to realize a photolithography device even when the photolithography device is tried to produce by using a conventional calcium fluoride crystal as an optical material and F2 laser as a light source, because the influence on absorption caused by lead is large in the wavelength of F2 laser.;SOLUTION: A method of producing a calcium fluoride single crystal comprises a first treatment process for adding a lead fluoride powder to a calcium fluoride powder and mixing the mixture, a second treatment process for keeping the resulting mixture at a specified temperature under a vacuum atmosphere, a third treatment process for allowing an evaporation reaction to occur at a specific temperature under a vacuum atmosphere, and further melting and crystallizing to form the single crystal. The calcium fluoride single crystal for vacuum ultraviolet optics, which contains lead in a concentration of ≤0.1 ppm and has transmission loss to light having the wave length of 153.4 nm of ≤0.5%/cm and transmission loss to light having the wave length of 157.6 nm of ≤0.3%/cm, is provided.;COPYRIGHT: (C)2002,JPO