PHOTOMASK SUBSTRATE MADE OF SYNTHETIC QUARTZ GLASS AND PHOTOMASK

摘要

It is to provide a photomask substrate which has a low birefringence and with which polarized illumination can be employed or immersion exposure can be carried out. A photomask substrate made of a synthetic quartz glass to be used for production of a semiconductor employing a light source having an exposure wavelength of at most about 200 nm, which has a birefringence of at most 1 nm/6.35 mm at the exposure wavelength, and of which the amount of decrease in light transmittance is at most 1.0% as a difference in light transmittance at a wavelength of 217 nm, between before and after irradiation with Xe excimer lamp with an illuminance of 13.2 mW/cm<2> for 20 minutes.