Method for determining laser-induced compaction in fused silica

• US 6,543,254 B2
• Filed: 09/26/2001
• Issued: 04/08/2003
• Est. Priority Date: 08/29/1996
• Status: Expired due to Fees

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Powell, William R., Seward, Thomas P. III, Smith, Charlene M., Borrelli, Nicholas F., Allan, Douglas C.
• Primary Examiner(s): VINCENT, SEAN E
• Application Number:
  US09/964,987
• Publication Number:
  US 20020036188A1
• Time in Patent Office: 559 Days
• Field of Search: 65/291.1, 65/332, 65D/IG.13, 653/92, 700/97, 700/98, 700/105, 700/157
• US Class Current: 65/29.11
• CPC Class Codes: C03B 19/06 by sintering, e.g. by cold isostatic pressing of powders and subsequent sintering, by hot pressing of powders, by sintering slurries or dispersions not undergoing a liquid phase reaction
• CPC Class Codes: C03B 19/066 for the production of quartz or fused silica articles other processes specially adapted for the production of quartz or fused silica articles C03B20/00
• CPC Class Codes: C03B 19/1065 by liquid phase reactions, e.g. by means of a gel phase
• CPC Class Codes: C03B 19/1453 Thermal after-treatment of the shaped article, e.g. dehydrating, consolidating, sintering
• CPC Class Codes: C03B 20/00 Processes specially adapted for the production of quartz or fused silica articles , not otherwise provided for C03B19/01, C03B19/066, C03B19/106, C03B19/12, C03B19/14, C03B37/00 take precedence
• CPC Class Codes: C03B 2207/32 Non-halide
• CPC Class Codes: C03C 1/006 to produce glass through wet route
• CPC Class Codes: C03C 2201/02 Pure silica glass, e.g. pure fused quartz
• CPC Class Codes: C03C 2203/50 After-treatment
• CPC Class Codes: C03C 23/0025 by a laser beam
• CPC Class Codes: C03C 3/06 with more than 90% silica by weight, e.g. quartz C03C3/045 takes precedence
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G03F 7/70216 Mask projection systems
• CPC Class Codes: G03F 7/70958 Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties
• CPC Class Codes: Y10S 65/13 Computer control

Abstract

The invention relates to fused silica having low compaction under high energy irradiation, particularly adaptable for use in photolithography applications.

Claims

1. 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.

2. The method of claim 1 wherein step (a) comprises:

(i) irradiating a sample of said fused silica glass with said given number of pulses and said given pulse fluence, said sample having a predetermined geometry and said pulses having a predetermined profile;

(ii) measuring at least one of;

(a) a change in optical path length as a result of the irradiation for at least one path through the sample, or

(b) a change in birefringence as a result of the irradiation for at least one path through the sample; and

(iii) determining the intrinsic densification from the measurements of step (ii) and a model of the response of a sample having the predetermined geometry to a pulse having the predetermined profile.

3. The method of claim 2 wherein the model is a finite-element model.

4. The method of claim 1 wherein step (b) is performed using a model for said lens.

5. The method of claim 4 wherein said model is a finite-element model.

14. The method of claim 1 wherein in step (a), a programmed computer is employed in determining the intrinsic densification of said fused silica glass.

6. 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.

7. The method of claim 6 wherein step (d) is performed using finite-element analysis.

15. The method of claim 6 wherein a programmed computer is employed in the modeling of step (d).

8. 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).

9. The method of claim 8 wherein step (a) comprises:

(i) irradiating a sample of said specified type of fused silica with a dose of laser light having a predetermined profile;

(ii) measuring at least one of;

(a) a change in optical path length as a result of the irradiation for at least one path through the sample, or

(b) a change in birefringence as a result of the irradiation for at least one path through the sample; and

(iii) determining the intrinsic densification from the measurements of step (ii) and a model of the response of a sample having the predetermined geometry to laser light having the predetermined profile.

10. The method of claim 9 wherein the dose is the expected lifetime exposure of the stepper lens to laser light in the photolithographic system.

11. The method of claim 9 wherein the model is a finite-element model.

12. The method of claim 8 wherein step (b) is performed using a model for said stepper lens.

13. The method claim 12 wherein said model is a finite-element model.

16. The method of claim 8 wherein in step (a), a programmed computer is employed in determining the intrinsic densification value for the specified type of fused silica.