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US 6,309,991 B1Granted
Silica with low compaction under high energy irradiation
AssigneeCorning Incorporated
InventorsNicholas F. Borrelli, Thomas P. Seward, III, Charlene Smith
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Abstract
Fused silica stepper lens for photolithographic application are disclosed which are resistant to laser-induced damage, specifically, compaction or densification which can lead to an increase in the optical path length of the lens. The figure compares the phase front distortions of a standard fused silica with the phase front distortions observed in two inventive stepper lens fused silica.
Claims2
A method for producing a fused silica stepper lens which is resistant to compaction when exposed to high intensity excimer radiation comprising the steps of:
- (a) depositing on a starting member a coating of flame hydrolysis-produced glass soot to form a soot preform;
- (b) consolidating the soot preform to form a dense glass layer free from particle boundaries;
- and
- (c) forming said dense glass layer into a stepper lens;
- said consolidation step being characterized in that it comprises heating said soot preform to a temperature within the consolidation temperature range for a time sufficient to cause said soot particles to fuse and form a dense glass layer, and simultaneously subjecting the soot preform to a stream of a substantially dry, hydrogen-free, chlorine containing atmosphere;
- wherein said method also comprises:
- (i) exposing a sample of fused silica made by steps (a) and (b) to high intensity excimer radiation;
- and
- (ii) determining the resulting compaction of said sample.
6 more elements
A process comprising:
- (I) producing a fused silica stepper lens which is resistant to compaction when exposed to high intensity excimer radiation by a method comprising:
- (a) depositing on a starting member a coating of flame hydrolysis-produced glass soot to form a soot preform;
- (b) consolidating the soot preform to form a dense glass layer free from particle boundaries;
- and
- (c) forming said dense glass layer into a stepper lens;
- said consolidation step being characterized in that it comprises heating said soot preform to a temperature within the consolidation temperature range for a time sufficient to cause said soot particles to fuse and form a dense glass layer, and simultaneously subjecting the soot preform to a stream of a substantially dry, hydrogen-free, chlorine containing atmosphere;
- and
- (II) using the stepper lens formed in step (c) to perform photolithography.
5 more elements
Dependencies are inferred from the claim text.