| 摘要 |
<p>PROBLEM TO BE SOLVED: To provide, as a method for cleaning a glass substrate for a photomask using a liquid mixture of a sulfuric acid and a hydrogen peroxide solution, a method for cleaning a glass substrate for a photomask capable of swiftly removing residual sulfuric acid following cleaning with the liquid mixture.SOLUTION: The provided cleaning method is a method for cleaning principal surfaces of a glass substrate for a photomask wherein the following steps are executed in proper order: a first step of cleaning principal surfaces of a glass substrate by using, as a cleaning liquid, a liquid mixture obtained by mixing a sulfuric acid having a concentration of at least 90 mass% and a hydrogen peroxide solution having a concentration of at least 20 mass% in a state where the volume ratio of the hydrogen peroxide solution with respect to the sulfuric acid (hydrogen peroxide solution/sulfuric acid) is 1 or below, a second step of rinsing the principal surfaces of the glass substrate by using a hydrogen peroxide solution having a concentration of at least 5 mass%, and a third step of rinsing the principal surfaces of the glass substrate by using pure water or ultrapure water.</p> |
