US5452090A
Expired / Lapsed
US
⏱️ 0.0 years remaining
CCD based confocal filtering for improved accuracy in x-ray proximity alignment
Assignee: International Business Machines Corp
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Filing: 1994-04-22
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Granted: 1995-09-19
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Expires: 2014-04-22
Abstract
Abstract In a reverse darkfield (RDF) microlithography alignment system a confocal spatial filtering system discriminates against topographical features other than the alignment mark. A CCD detector array provides flexible confocal filtering via a pixel weighting matched to the optical system. The confocal filtering system employs empirical filter optimization accomplished by correlating stored images with resulting overlays. The empirical optimization of the filter reweights the CCD array and correlates back to measured overlay results. This not only enhances the proven process insensitivity of RDF systems, but combines it with the improved resolution and noise rejection of confocal imaging. Alternatively the means for confocal spatial filtering is comprised of a filter matched to the instantaneous image of an alignment target; for example, a double slit filter matched to the image of a single alignment mark edge.
Inventors
- 👤 Christopher J. Progler
- 👤 Alan E. Rosenbluth
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:36
CPC Classifications
G; G03; G03F; G03F9/00; G03F9/70; G03F9/7069; G03F7/00; G03F7/70; G03F7/70483; G03F7/70605; G03F7/70616; G03F7/70633; G03F9/7088
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
94 words
A microlithography system comprising: illumination means for projecting a sharp image of a subresolution aperture onto an alignment target; means for scanning said alignment target through said sharp image at a plurality of scan positions; means for blocking collection of light directly reflected from said alignment target; collection means for collecting light scattered from the vicinity of said alignment target at each said scan position; and detection means for integrating and filtering said collected light, said integrated collected light being filtered to provide an alignment signal pulse at an edge of an alignment pattern.
Claim 2
Dependent Claim
94 words
A microlithography system comprising: illumination means for projecting a sharp image of a subresolution aperture onto an alignment target; means for scanning said alignment target through said sharp image at a plurality of scan positions; means for blocking collection of light directly reflected from said alignment target; collection means for collecting light scattered from the vicinity of said alignment target at each said scan position; and detection means for integrating and filtering said collected light, said integrated collected light being filtered to provide an alignment signal pulse at an edge of an alignment pattern.
Claim 3
Dependent Claim
19 words
A microlithography alignment system as in claim 1 wherein said detection means comprises a two dimensional CCD detector array.
Claim 4
Dependent Claim
18 words
A microlithography system as in claim 1 wherein said detection means comprises a two dimensional diode array detector.
Claim 5
Dependent Claim
19 words
A microlithography alignment system as in claim 1 wherein said collection means comprises a darkfield collection lens pupil aperture.
Claim 6
Dependent Claim
13 words
A microlithography system as in claim 4 wherein said aperture is a slit.
Claim 7
Dependent Claim
15 words
A microlithography system as in claim 5 wherein said aperture comprises a pair of slits.
Claim 8
Dependent Claim
19 words
A microlithography alignment system as in claim 6 wherein said detection means comprises a two dimensional CCD detector array.
Claim 9
Dependent Claim
166 words
A microlithography exposure arrangement comprising: an illumination source; a subresolution aperture; a Reverse Darkfield (RDF) mirror; an aperture in said RDF mirror; an imaging lens, whereby light from said illumination source is passed through and shaped by said subresolution aperture, then passed through said RDF mirror aperture to said imaging lens and focussed by said imaging lens into a beam, said beam being directed by said imaging lens through a mask to a wafer and reflected therefrom; a tube lens; a confocal aperture; a relay lens; and, a detector, whereby said reflected beam is passed back through said imaging lens to said RDF mirror, a portion of said reflected beam being reflected by said RDF mirror at an angle to said reflected beam, said portion being passed through and focussed by said tube lens and forming a second beam, said second beam being directed to and passing through said confocal aperture to said relay lens, said relay lens refocussing and directing said beam onto said detector.
Claim 10
Dependent Claim
166 words
A microlithography exposure arrangement comprising: an illumination source; a subresolution aperture; a Reverse Darkfield (RDF) mirror; an aperture in said RDF mirror; an imaging lens, whereby light from said illumination source is passed through and shaped by said subresolution aperture, then passed through said RDF mirror aperture to said imaging lens and focussed by said imaging lens into a beam, said beam being directed by said imaging lens through a mask to a wafer and reflected therefrom; a tube lens; a confocal aperture; a relay lens; and, a detector, whereby said reflected beam is passed back through said imaging lens to said RDF mirror, a portion of said reflected beam being reflected by said RDF mirror at an angle to said reflected beam, said portion being passed through and focussed by said tube lens and forming a second beam, said second beam being directed to and passing through said confocal aperture to said relay lens, said relay lens refocussing and directing said beam onto said detector.
Claim 11
Dependent Claim
12 words
The arrangement of claim 8 wherein said detector is a photo-multiplier tube.
Claim 12
Dependent Claim
155 words
A microlithography exposure arrangement comprising: an illumination source; a subresolution aperture; a Reverse Darkfield (RDF) mirror; an aperture in said RDF mirror; an imaging lens, whereby light from said illumination source is passed through and shaped by said subresolution aperture, then passed through said RDF mirror aperture to said imaging lens and focussed by said imaging lens into a beam, said beam being directed by said imaging lens through a mask to a wafer and reflected therefrom; a tube lens; a relay lens; and a detector, whereby said reflected beam is passed through said imaging lens to said RDF mirror, a portion of said reflected beam being reflected by said RDF mirror at an angle to said reflected beam, said portion being passed through and focussed by said tube lens and forming a second beam, said second beam being directed to said relay lens, said relay lens refocussing and directing said beam onto said detector.
Claim 13
Dependent Claim
155 words
A microlithography exposure arrangement comprising: an illumination source; a subresolution aperture; a Reverse Darkfield (RDF) mirror; an aperture in said RDF mirror; an imaging lens, whereby light from said illumination source is passed through and shaped by said subresolution aperture, then passed through said RDF mirror aperture to said imaging lens and focussed by said imaging lens into a beam, said beam being directed by said imaging lens through a mask to a wafer and reflected therefrom; a tube lens; a relay lens; and a detector, whereby said reflected beam is passed through said imaging lens to said RDF mirror, a portion of said reflected beam being reflected by said RDF mirror at an angle to said reflected beam, said portion being passed through and focussed by said tube lens and forming a second beam, said second beam being directed to said relay lens, said relay lens refocussing and directing said beam onto said detector.
Claim 14
Dependent Claim
13 words
The arrangement of claim 10 wherein said detector is a CCD virtual filter.
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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) | 1998-09-18 | 1999-03-20 | 1999-09-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-09-18 | 2003-03-20 | 2003-09-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-09-18 | 2007-03-20 | 2007-09-19 | $7700.00 | Window Closed / Lapsed |