US4637714A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Inspection system for pellicalized reticles
Assignee: International Business Machines Corp
•
Filing: 1985-10-31
•
Granted: 1987-01-20
•
Expires: 2005-10-31
Abstract
Abstract A method of detecting defects in a reticle used to fabricate semiconductor circuits by enhancing the image of a defect in one chip site without appreciably changing all other chip site images. In a step-and-repeat alignment system, a first chip site is exposed under normal intensities to print the reticle pattern at a proper exposure level. At a second chip site, exposure takes place using the same reticle (or a second identical reticle) at lower intensity levels. Given this underexposure, residual photoresist will remain at defect sites. The optical imagery at the two chip sites is different allowing comparator techniques to be used.
Inventors
- 👤 Alexander L. Flamholz
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 18:11
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/68; G03F1/82; G03F1/84; G03F7/00; G03F7/70; G03F7/70483; G03F7/70605; G03F7/70616; G03F1/62
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
101 words
A method of detecting defects in a step-and-repeat projection system for imaging patterns from a reticle subject to contamination onto a substrate comprising the steps of: exposing a first site on said substrate coated with a photosensitive film to radiation through said reticle to achieve a first exposure condition; exposing a second site on said substrate coated with said photosensitive film to radiation to achieve a second exposure condition; and comparing by an optical comparator the first and second sites to identify the presence and location of defects by a difference in optical imagery existing at said first and second sites.
Claim 2
Independent Claim
101 words
A method of detecting defects in a step-and-repeat projection system for imaging patterns from a reticle subject to contamination onto a substrate comprising the steps of: exposing a first site on said substrate coated with a photosensitive film to radiation through said reticle to achieve a first exposure condition; exposing a second site on said substrate coated with said photosensitive film to radiation to achieve a second exposure condition; and comparing by an optical comparator the first and second sites to identify the presence and location of defects by a difference in optical imagery existing at said first and second sites.
Claim 3
Dependent Claim
30 words
The method of claim 1 wherein said first exposure condition is a full exposure of said photosensitive film and said second exposure condition is an underexposure of said photosensitive film.
Claim 4
Dependent Claim
16 words
The method of claim 2 wherein said underexposure is approximately 10% less than a full exposure.
Claim 5
Dependent Claim
31 words
The method of claim 1 wherein prior to exposure said first and second sites are defined on said substrates at different locations and said substrate is coated with said photosensitive film.
Claim 6
Dependent Claim
29 words
The method of claim 4 wherein said photosensitive film is a photosensitive resist and said resist is developed to obtain a residual film at said first and second sites.
Claim 7
Dependent Claim
24 words
The method of claim 5 wherein said residual film at a defect site is a color and shape different than at a defect-free site.
Claim 8
Dependent Claim
44 words
The method of claim 1 wherein said first exposure condition is a full exposure of said first chip site at a first time and said second exposure condition is an underexposure of said second chip at a second time subsequent to said first time.
Claim 9
Dependent Claim
30 words
The method of claim 7 wherein said first and second chip sites are defined on said substrate and differet locations and wherein said substrate is coated with said photosensitive film.
Claim 10
Dependent Claim
16 words
The method of claim 7 wherein said underexposure is approximately 10% less than a full exposure.
Claim 11
Dependent Claim
21 words
The method of claim 7 wherein said first and second chip sites are in different columns of rows of chip sites.
Claim 12
Dependent Claim
24 words
The method of claim 7 wherein said residual film at a defect site is a color and shape different than at a defect-free site.
Claim 13
Dependent Claim
21 words
The method of claim 1 wherein said second exposure condition occurs by exposing said second site to radiation through said reticle.
Claim 14
Dependent Claim
21 words
The method of claim 7 wherein said second exposure condition occurs by exposing said second site to radiation through said reticle.
Claim 15
Dependent Claim
31 words
The method of claim 1 wherein said second exposure condition occurs by exposing said second site to radiation through a second reticle different from said reticle but having the same pattern.
References Cited (Backward Citations)
US3819265A
Cited
US4239384A
Cited
US4131363A
Cited
US4335956A
Cited
US4443096A
Cited
US4416539A
Cited
US4577961A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-01-19 | 1990-07-21 | 1991-01-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-01-19 | 1994-07-21 | 1995-01-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-01-19 | 1998-07-21 | 1999-01-20 | $7700.00 | Window Closed / Lapsed |