Patent ID: 6295841
Filing Date: 2001-10-02
Classification: C03B,C03C,G03F,Y10S

Abstract:
A method for making a fused silica stepper lens for use in a photolithographic system, said lens being resistant to laser-induced densification, and said system having a predetermined expected life at an estimated excimer laser irradiation dose, the method comprising:(a) selecting a fused silica for the stepper lens;(b) determining an intrinsic densification value for the selected fused silica for the estimated excimer laser irradiation dose;(c) calculating the expected total densification of the lens using the intrinsic densification value determined in step (b);(d) pre-densifying a blank of the selected fused silica based on the expected total densification calculated in step (c); and(e) producing the stepper lens from the pre-densified blank.