Method for determining laser-induced compaction in fused silica
AssigneeCorning Incorporated
InventorsDouglas C. Allan, Nicholas F. Borrelli, William R. Powell, Thomas P. Seward, III, Charlene M. Smith
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Abstract
The invention relates to fused silica having low compaction under high energy irradiation, particularly adaptable for use in photolithography applications.
Claims16
A method for predicting the optical path distortion of a fused silica glass lens under actual photolithographic use conditions comprising:
- (a) determining the intrinsic densification of said fused silica glass for a given number of pulses and a given pulse fluence;
- and
- (b) predicting the optical path distortion of said lens for said given number of pulses and given pulse fluence using said intrinsic densification.
A method for parameterizing the response of a fused silica glass of a specified type to laser light of a specified dose comprising:
- (a) selecting a geometry for a sample of the glass;
- (b) selecting a laser beam profile for irradiating the sample with the specified dose;
- (c) irradiating a sample of the glass having the geometry selected in step (a) with a laser beam having the specified dose and the profile selected in step (b) and measuring at least one of:
- (i) a change in optical path length as a result of the irradiation for at least one path through the sample, or
- (ii) a change in birefringence as a result of the irradiation for at least one path through the sample;
- (d) modeling the response of a sample having the geometry selected in step (a) to a laser beam having the profile selected in step (b);
- and
- (e) determining an intrinsic densification value for the glass from the at least one measurement of step (c) and the modeling of step (d), said value being a parameter which characterizes the response of the glass to laser light having the specified dose.
A method for producing a stepper lens for use in a photolithographic system, said stepper lens being composed of a specified type of fused silica, said method comprising:
- (a) determining an intrinsic densification value for the specified type of fused silica;
- (b) designing the stepper lens to have a predicted lifetime densification using said intrinsic densification value of step (a);
- and
- (c) producing the stepper lens designed in step (b).
Dependencies are inferred from the claim text.