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US3630596A
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Photomask regeneration by intensity spatial filtering
Assignee: AT&T Inc
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Filing: 1969-09-30
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Granted: 1971-12-28
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Expires: 1989-09-30
Abstract
Abstract An intensity-type spatial filtering technique is employed to generate a corrected replica of a two-dimensional photomask or other pattern containing an array of regularly spaced elements which exhibit nonperiodic errors. A coherent beam of light is diffracted by the mask and focused onto a transparency containing an array of discrete transparent regions against an opaque background. The regions are spaced by a distance inversely proportional to the element spacing on the pattern. The focused light is spatially modulated by the transparency to suppress nonperiodic information contained in the focused light. The spatially modulated light transmitted by the filter is refocused on a photosensitive film which, when developed, defines an array of elements corresponding exactly to the array on the test pattern with the nonperiodic errors removed.
Inventors
- 👤 Laurence S Watkins
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 15:49
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/68; G03F1/72; G02; G02B; G02B27/00; G02B27/42; G02B27/46
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
99 words
A method of suppressing nonperiodic errors in a twodimensional array of nominally identical elements mutually spaced apart by a predetermined distance, which comprises the steps of: directing a spatially coherent beam of light at the array to diffract the light; focusing the diffracted light on a filter containing a plurality of discrete transparent regions on an opaque field, the transparent regions being spaced by a distance inversely proportional to the predetermined distance to spatially modulate the intensity of the focused light; and reimaging the spatially modulated light to form an image of thE array with the nonperiodic errors removed.
Claim 2
Independent Claim
99 words
A method of suppressing nonperiodic errors in a twodimensional array of nominally identical elements mutually spaced apart by a predetermined distance, which comprises the steps of: directing a spatially coherent beam of light at the array to diffract the light; focusing the diffracted light on a filter containing a plurality of discrete transparent regions on an opaque field, the transparent regions being spaced by a distance inversely proportional to the predetermined distance to spatially modulate the intensity of the focused light; and reimaging the spatially modulated light to form an image of thE array with the nonperiodic errors removed.
Claim 3
Dependent Claim
21 words
A method as defined in claim 1 in which the directing step is accomplished with a photomask as the two-dimensional array.
Claim 4
Dependent Claim
130 words
A regenerative method of correcting nonperiodic errors on a two-dimensional test array of nominally identical elements mutually spaced apart by a predetermined distance, which comprises the steps of: directing a spatially coherent beam of light at the test array to diffract the light; focusing the diffracted light on a filter containing a plurality of discrete transparent regions on an opaque field, the transparent regions being distributed in accordance with the interference function of the array and spaced by a distance inversely proportional to the predetermined distance to spatially modulate the intensity of the focused light; reimaging the spatially modulated light; and exposing a photosensitive surface to the reimaged light to define, on the surface, a regular array of elements corresponding to the test array but without the nonperiodic errors thereon.
Claim 5
Dependent Claim
130 words
A regenerative method of correcting nonperiodic errors on a two-dimensional test array of nominally identical elements mutually spaced apart by a predetermined distance, which comprises the steps of: directing a spatially coherent beam of light at the test array to diffract the light; focusing the diffracted light on a filter containing a plurality of discrete transparent regions on an opaque field, the transparent regions being distributed in accordance with the interference function of the array and spaced by a distance inversely proportional to the predetermined distance to spatially modulate the intensity of the focused light; reimaging the spatially modulated light; and exposing a photosensitive surface to the reimaged light to define, on the surface, a regular array of elements corresponding to the test array but without the nonperiodic errors thereon.
Claim 6
Dependent Claim
177 words
Apparatus for producing an error-free replica of a two-dimensional test array of normally identical elements nominally spaced apart by a predetermined distance but susceptible to nonperiodic errors, which comprises: means for directing spatially coherent beams of light as the test array to diffract the light; a first lens positioned to focus the light diffracted by the test array; a planar optical filter containing a distribution of discrete transparent regions on an opaque field, the transparent regions being distributed in accordance with the interference function of the array and spaced by a distance inversely proportional to the predetermined distance, the filter being positioned at the focal plane of the first lens for spatially modulating the light focused by the first lens; a second lens positioned to reimage the light spatially modulated by the filter; and a photosensitive surface located at the focal plane of the second lens for receiving the light focused thereby, the last-mentioned light exposing the surface in a pattern defining an array of elements corresponding to the test array but without the nonperiodic errors thereon.
Claim 7
Dependent Claim
177 words
Apparatus for producing an error-free replica of a two-dimensional test array of normally identical elements nominally spaced apart by a predetermined distance but susceptible to nonperiodic errors, which comprises: means for directing spatially coherent beams of light as the test array to diffract the light; a first lens positioned to focus the light diffracted by the test array; a planar optical filter containing a distribution of discrete transparent regions on an opaque field, the transparent regions being distributed in accordance with the interference function of the array and spaced by a distance inversely proportional to the predetermined distance, the filter being positioned at the focal plane of the first lens for spatially modulating the light focused by the first lens; a second lens positioned to reimage the light spatially modulated by the filter; and a photosensitive surface located at the focal plane of the second lens for receiving the light focused thereby, the last-mentioned light exposing the surface in a pattern defining an array of elements corresponding to the test array but without the nonperiodic errors thereon.
Claim 8
Independent Claim
201 words
A method of manufacturing a photomask free of nonperiodic error, for use in the fabrication of integrated electronic circuits, and the like, said photomask comprising a two-dimensional array of nominally identical mask features, mutually spaced apart by a predetermined distance, comprising the steps of: directing a spatially coherent beam of radiant energy at a defective photomask, which comprises a two-dimensional array of nominally identical mask features, mutually spaced apart by a predetermined distance but which is known to include at least one nonperiodic error, to diffract the radiant energy; focusing the diffracted radiant energy onto a filter containing a plurality of discrete regions which are transparent, to said radiant energy, on an opaque field, said transparent regions being distributed in accordance with the interference function of the array and spaced apart by a distance inversely proportional to said predetermined distance, to spatially modulate the intensity of the focused radiant energy; reimaging the spatially modulated radiant energy 20 to expose a surface sensitive to said radiant energy, to define of said surface a regular array of photomask features corresponding to the features on the defective mask, but which has said at least one nonperiodic error removed, whereby said error-free photomask is produced.
Claim 9
Independent Claim
201 words
A method of manufacturing a photomask free of nonperiodic error, for use in the fabrication of integrated electronic circuits, and the like, said photomask comprising a two-dimensional array of nominally identical mask features, mutually spaced apart by a predetermined distance, comprising the steps of: directing a spatially coherent beam of radiant energy at a defective photomask, which comprises a two-dimensional array of nominally identical mask features, mutually spaced apart by a predetermined distance but which is known to include at least one nonperiodic error, to diffract the radiant energy; focusing the diffracted radiant energy onto a filter containing a plurality of discrete regions which are transparent, to said radiant energy, on an opaque field, said transparent regions being distributed in accordance with the interference function of the array and spaced apart by a distance inversely proportional to said predetermined distance, to spatially modulate the intensity of the focused radiant energy; reimaging the spatially modulated radiant energy 20 to expose a surface sensitive to said radiant energy, to define of said surface a regular array of photomask features corresponding to the features on the defective mask, but which has said at least one nonperiodic error removed, whereby said error-free photomask is produced.
References Cited (Backward Citations)
US3370268A
Cited
US3409872A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-27 | 1975-06-28 | 1975-12-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-27 | 1979-06-28 | 1979-12-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-27 | 1983-06-28 | 1983-12-28 | $7700.00 | Window Closed / Lapsed |