US5508803A
Expired / Lapsed
US
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Method and apparatus for monitoring lithographic exposure
Assignee: International Business Machines Corp
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Filing: 1994-12-20
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Granted: 1996-04-16
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Expires: 2014-12-20
Abstract
Abstract A lithographic mask with an exposure monitor for imaging a gray scale feature. The exposure monitor has abutting regions of differing optical density disposed on the mask for imaging the gray scale feature by taking advantage of diffraction effects. After calibrating gray scale feature size to critical feature size, a gray scale feature may be imaged to monitor critical feature size due to exposure.
Inventors
- 👤 Michael S. Hibbs
- 👤 William C. Joyce
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 22:26
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70483; G03F7/7055; G03F7/70558; G03F1/00; G03F1/38; G03F1/44; G03F1/50; G03F7/70605; G03F7/70616; G03F7/70625
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
63 words
An exposure monitor for imaging a gray scale feature, said exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto, wherein diffractive blurring through said plurality of abutting regions provides a continuous light distribution in said gray scale feature.
Claim 2
Dependent Claim
63 words
An exposure monitor for imaging a gray scale feature, said exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto, wherein diffractive blurring through said plurality of abutting regions provides a continuous light distribution in said gray scale feature.
Claim 3
Dependent Claim
35 words
The exposure monitor of claim 1, wherein said exposure monitor comprises a substrate and a plurality of patches of different sizes and optical transmissivities layered on said substrate to create said plurality of abutting regions.
Claim 4
Dependent Claim
15 words
The exposure monitor of claim 2 wherein said plurality of patches comprises a carbon patch.
Claim 5
Dependent Claim
59 words
The exposure monitor of claim 1, wherein said exposure monitor comprises a substrate and wherein said plurality of abutting regions comprises: a first patch of film on said substrate having a first optical density; and a second patch of film on said substrate abutting said first patch and having a second optical density different than said first optical density.
Claim 6
Dependent Claim
19 words
The exposure monitor of claim 4 wherein said first patch and said second patch each comprise a carbon patch.
Claim 7
Dependent Claim
22 words
The exposure monitor of claim 1, wherein imaging of each of said plurality of abutting regions is exposure sensitive and focus insensitive.
Claim 8
Dependent Claim
79 words
A semiconductor wafer comprising an imaged gray scale feature for monitoring exposure within a lithographic system, wherein said imaged gray scale feature was imaged with an exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto, wherein diffractive blurring through said plurality of abutting regions provides a continuous light distribution in said gray scale feature.
Claim 9
Dependent Claim
79 words
A semiconductor wafer comprising an imaged gray scale feature for monitoring exposure within a lithographic system, wherein said imaged gray scale feature was imaged with an exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto, wherein diffractive blurring through said plurality of abutting regions provides a continuous light distribution in said gray scale feature.
Claim 10
Dependent Claim
33 words
The semiconductor wafer of claim 7 further comprising an imaged critical feature, wherein size of said imaged gray scale feature is indicative of size of said imaged critical feature due to said exposure.
Claim 11
Independent Claim
126 words
A method for monitoring exposure in a lithographic system, said method comprising steps of: calibrating exposure in said lithographic system such that size of an imaged gray scale feature is indicative of size of an imaged critical feature; imaging a critical feature and a gray scale feature in a layer of light-sensitive material coated on a substrate, wherein said gray scale feature is imaged with an exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto, wherein diffractive blurring through said plurality of abutting regions provides a continuous light distribution in said gray scale feature; and measuring said imaged gray scale feature.
Claim 12
Independent Claim
126 words
A method for monitoring exposure in a lithographic system, said method comprising steps of: calibrating exposure in said lithographic system such that size of an imaged gray scale feature is indicative of size of an imaged critical feature; imaging a critical feature and a gray scale feature in a layer of light-sensitive material coated on a substrate, wherein said gray scale feature is imaged with an exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto, wherein diffractive blurring through said plurality of abutting regions provides a continuous light distribution in said gray scale feature; and measuring said imaged gray scale feature.
Claim 13
Dependent Claim
148 words
The method of claim 9, wherein said step of calibrating comprises steps of: imaging in a layer of light-sensitive material coated on a substrate a critical feature at a plurality of exposure levels; imaging in said layer of light-sensitive material a gray scale feature at said plurality of exposure levels wherein said gray scale feature is imaged with an exposure monitor comprising a plurality of abutting regions, each of said plurality of abutting regions having an optical density different from that of each other of said plurality of abutting regions immediately adjacent thereto; measuring each said imaged gray scale feature and correlating gray scale feature size to exposure level to obtain gray scale exposure data; measuring each said imaged critical feature and correlating critical feature size to exposure level to obtain critical feature exposure data; and cross-correlating said gray scale exposure data and said critical feature exposure data.
Claim 14
Dependent Claim
13 words
The method of claim 9 wherein said step of measuring comprises optically measuring.
References Cited (Backward Citations)
US4183990A
Cited
US4575124A
Cited
US4588298A
Cited
US4788433A
Cited
US4902899A
Cited
US5124927A
Cited
US5213916A
Cited
US5276337A
Cited
US5300786A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-04-16 | 1999-10-16 | 2000-04-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-16 | 2003-10-16 | 2004-04-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-04-16 | 2007-10-16 | 2008-04-16 | $7700.00 | Window Closed / Lapsed |