US3614232A
Expired / Lapsed
US
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Pattern defect sensing using error free blocking spacial filter
Assignee: International Business Machines Corp
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Filing: 1968-11-25
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Granted: 1971-10-19
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Expires: 1988-11-25
Abstract
Abstract Defects in microcircuit patterns are sensed by illuminating the pattern with monochromatic collimated light. The illuminated pattern is imaged through a lens to produce substantially a twodimensional optical Fourier transform of the pattern at a plane on the output side of the lens. An optical filter (transparency) which includes substantially the negative of the Fourier transform of a defect-free specimen of the microcircuit is placed at the aforesaid plane to block the optical frequency components corresponding to the defect-free specimen. Light passing through the filter is processed to provide various indications of the pattern defects.
Inventors
- 👤 Einar S Mathisen
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 14:48
CPC Classifications
G; G02; G02B; G02B27/00; G02B27/42; G02B27/46; G01; G01N; G01N21/00; G01N21/84; G01N21/88; G01N21/95; G01N21/956; G01N21/95623
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
104 words
Apparatus for determining the presence of defects in a specimen pattern comprising: a source of monochromatic collimated light for illuminating said pattern, optical means for generating from said pattern an image representing substantially the Fourier transform of said pattern, optical filter means receiving said image for blocking spatial frequency components of said image, said filter means comprising a pattern having relatively transparent and relatively opaque portions, the relatively opaque portion conforming to substantially the Fourier transform of an error-free reference pattern corresponding to said specimen pattern, and detector means for detecting the spatial frequency components of said image not blocked by said filter means.
Claim 2
Dependent Claim
104 words
Apparatus for determining the presence of defects in a specimen pattern comprising: a source of monochromatic collimated light for illuminating said pattern, optical means for generating from said pattern an image representing substantially the Fourier transform of said pattern, optical filter means receiving said image for blocking spatial frequency components of said image, said filter means comprising a pattern having relatively transparent and relatively opaque portions, the relatively opaque portion conforming to substantially the Fourier transform of an error-free reference pattern corresponding to said specimen pattern, and detector means for detecting the spatial frequency components of said image not blocked by said filter means.
Claim 3
Dependent Claim
13 words
Apparatus as defined in claim 1 wherein said pattern is a microcircuit mask.
Claim 4
Dependent Claim
23 words
Apparatus as defined in claim 1 wherein said specimen, said filter means and said photodetector means lie substantially along the same optical axis.
Claim 5
Dependent Claim
111 words
Apparatus for determining the presence of defects in a specimen pattern comprising: a source of monochromatic collimated light for illuminating said pattern, optical means for generating from said pattern an image representing substantially the Fourier transform of said pattern, optical filter means receiving said image for blocking spacial frequency components for said image, said filter means comprising a composite of a diffraction grating pattern and a pattern having relatively transparent and relaTively opaque portions, the relatively opaque portion conforming to the Fourier transform of an error-free reference pattern corresponding to said specimen pattern, and detector means for detecting the spacial frequency components of said image not blocked by said filter means.
Claim 6
Dependent Claim
111 words
Apparatus for determining the presence of defects in a specimen pattern comprising: a source of monochromatic collimated light for illuminating said pattern, optical means for generating from said pattern an image representing substantially the Fourier transform of said pattern, optical filter means receiving said image for blocking spacial frequency components for said image, said filter means comprising a composite of a diffraction grating pattern and a pattern having relatively transparent and relaTively opaque portions, the relatively opaque portion conforming to the Fourier transform of an error-free reference pattern corresponding to said specimen pattern, and detector means for detecting the spacial frequency components of said image not blocked by said filter means.
Claim 7
Dependent Claim
29 words
Apparatus as defined in claim 4 wherein said specimen and said filter means lie along an optical axis inclined with respect to the optical axis of said photodetector means.
Claim 8
Dependent Claim
62 words
Apparatus as defined in claim 4 and further including means coupled to said detector means for producing signals representing the spatial coordinates of the portion of said pattern specimen which produces said spatial frequency components of said image not blocked by said filter means, and means receiving said signals for responding only to those signals, if any, which represent predetermined spatial coordinates.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-10-18 | 1975-04-19 | 1975-10-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-10-18 | 1979-04-19 | 1979-10-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-10-18 | 1983-04-19 | 1983-10-19 | $7700.00 | Window Closed / Lapsed |