Patent US4645338A successfully refreshed from Google Patents.
US4645338A
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Optical system for focus correction for a lithographic tool
Assignee: International Business Machines Corp
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Filing: 1985-04-26
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Granted: 1987-02-24
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Expires: 2005-04-26
Abstract
Abstract An apparatus and process for determining focus correction for a lithographic tool are provided. A periodic surface relief structure containing focus information is illuminated so that diffraction beams are generated. An object is translated orthogonally to the periodic structure to cause a change in the intensity of the diffracted beams. Focus correction is determined based upon the changes in the intensity of the diffracted beams.
Inventors
- 👤 Anthony Juliana, Jr.
- 👤 Milton R. Latta
- 👤 Glenn V. Sincerbox
- 👤 Carlton G. Willson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 14:04
CPC Classifications
G; G03; G03F; G03F9/00; G03F9/70; G03F9/7049
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
93 words
An optical system apparatus for focus correction for a lithographic tool, said apparatus comprising: (1) means for illuminating a periodic surface relief structure containing focus information which is on an object created in said lithographic tool, so that diffraction beams are generated, (2) means for translating the object orthogonally to the periodic structure, to cause a change in the intensity of the diffracted beams, (3) means for detecting the intensity of said diffracted beams, and (4) means for determining the focus correction based upon the changes in the intensity of the diffracted beams.
Claim 2
Dependent Claim
93 words
An optical system apparatus for focus correction for a lithographic tool, said apparatus comprising: (1) means for illuminating a periodic surface relief structure containing focus information which is on an object created in said lithographic tool, so that diffraction beams are generated, (2) means for translating the object orthogonally to the periodic structure, to cause a change in the intensity of the diffracted beams, (3) means for detecting the intensity of said diffracted beams, and (4) means for determining the focus correction based upon the changes in the intensity of the diffracted beams.
Claim 3
Dependent Claim
15 words
An apparatus as claimed in claim 1 wherein said means for illuminating is a laser.
Claim 4
Dependent Claim
16 words
An apparatus as claimed in claim 1 wherein the periodic surface relief structure is a photoresist.
Claim 5
Dependent Claim
29 words
An apparatus as claimed in claim 1 wherein said means for detecting is a broad area photodetector detecting multiple plus and minus diffraction orders and excluding the zero order.
Claim 6
Dependent Claim
18 words
An apparatus as claimed in claim 1 wherein a plurality of illumination beams and corresponding detectors are used.
Claim 7
Dependent Claim
87 words
An optical process for focus correction for a lithographic tool, said process comprising the steps: (1) illuminating a periodic surface relief structure containing focus information which is on an object created in said lithographic tool, so that diffraction beams are generated, (2) translating the object orthogonally to the periodic structure, to cause a change in the intensity of the diffracted beams, (3) detecting the intensity of the said diffracted beams, and (4) determining the focus correction based upon the changes in the intensity of the diffracted beams.
Claim 8
Dependent Claim
87 words
An optical process for focus correction for a lithographic tool, said process comprising the steps: (1) illuminating a periodic surface relief structure containing focus information which is on an object created in said lithographic tool, so that diffraction beams are generated, (2) translating the object orthogonally to the periodic structure, to cause a change in the intensity of the diffracted beams, (3) detecting the intensity of the said diffracted beams, and (4) determining the focus correction based upon the changes in the intensity of the diffracted beams.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-02-23 | 1990-08-25 | 1991-02-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-23 | 1994-08-25 | 1995-02-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-23 | 1998-08-25 | 1999-02-24 | $7700.00 | Window Closed / Lapsed |