US Patent 7622050 Process for polishing glass substrate

A process for polishing a glass substrate required to have high-degree of flatness and smoothness, is provided. A preliminarily polished glass substrate is applied with a surface treatment by a first-step gas-cluster ion beam etching to improve the flatness, and then, the glass substrate is applied with a surface treatment by a second-step gas-cluster ion beam etching having different irradiation conditions of those of the first-step gas-cluster ion beam etching to improve the surface roughness, whereby the glass substrate is finish-polished to have a flatness of at most 0.05 μm and a surface roughness (Rms) of at most 0.25 nm.