Patent ID: 7827824

Claim:
A method for preparing a synthetic quartz glass substrate for use with excimer lasers, comprising the steps of: (1) holding a synthetic quartz glass ingot, which is produced by a VAD soot process, at a temperature of 1,000° C. to 1,200° C. for at least 10 hours, raising the temperature in the range of 1,300° C. to 1600° C. over a time of at least 5 hours, and holding the ingot at the temperature for 1 to 5 hours; (2) hot shaping the ingot at a temperature in the range of 1,700° C. to 1,900° C. into a block of desired shape; (3) annealing the block at a temperature in the range of 1,000° C. to 1,300° C.; (4) slicing the block into a synthetic quartz glass substrate with a predetermined thickness; and (5) heat treating the substrate in a hydrogen atmosphere at or above atmospheric pressure and a temperature in the range of 200° C. to 500° C. for a time.