METHOD FOR FINISHING SURFACE OF PRELIMINARY POLISHED GLASS SUBSTRATE

摘要

This invention provides a method for finishing the surface of a glass substrate by removing waviness produced in preliminary polishing on the surface of the glass substrate to provide a highly flat surface. The surface of a preliminary polished quartz glass substrate containing a dopant and composed mainly of SiO₂ is finished by any method selected from ion beam etching, gas cluster ion beam etching, and plasma etching. In this case, conditions for finishing of the glass substrate surface are set for each site of the glass substrate, based on the results obtained from the step of measuring the flatness of the glass substrate surfaceusing shape measuring means comprising a low coherent light source, a pass match passage part, and an interference optical system, to measure the concentration distribution of a dopant contained in the glass substrate and to measure the flatness of the glass substrate surface, and the step of measuring the concentration distribution of the dopant contained in the glass substrate. Thereafter, the finishing is carried out under the determined finishing conditions while maintaining the angle of the normal of the glass substrate to a beam incident on the glass substrate surface at 30 to 89 degrees.