PRODUCTION OF SYNTHETIC QUARTZ GLASS FOR ArF EXCIMER LASER LITHOGRAPHY

摘要

PROBLEM TO BE SOLVED: To obtain an optical material excellent in homogeneity and having a high transmittance by irradiating a homogenized synthetic quartz glass with the Na content specified with the UV of specified wavelength under controlled conditions. SOLUTION: A synthetic quartz glass contg. 24-60 ppb Na is homogenized. The synthetic quartz glass is irradiated with the UV of <=260 nm wavelength for a time expressed by Y=(80X-1880)/z. In the expression, X is the Na concentration (ppb), Y is the irradiating time (hour), and Z is the illuminance (mW/cm2) of the UV on the irradiated face. A low-pressure mercury lamp of 253.7 and 184.9 nm dominant wavelength, an Xe excimer lamp of 172 nm wavelength or a KrCl excimer lamp of 222 nm wavelength is exemplified as the lamp to be used in UV irradiation. The surface roughness Rmax of the synthetic quartz glass to be irradiated with UV is preferably controlled to <=30μm.