US3697178A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of projection printing photoresist masking layers, including elimination of spurious diffraction-associated patterns from the print
Assignee: RCA Corp
•
Filing: 1971-11-01
•
Granted: 1972-10-10
•
Expires: 1991-11-01
Abstract
Abstract A substrate covered with photoresist is positioned in a parallel, spaced, fixed relationship to a photomask to form a photomask assembly. Then, the photoresist is exposed to a diffraction image of the photomask by projecting collimated light through the photomask. The diffraction image comprises a primary image and a spurious, diffraction-associated secondary image. The light is projected with an oblique orientation to the photomask. The oblique orientation is varied during the exposing to selectively prevent the secondary image from resulting in the uncovering of corresponding areas of the substrate upon development. Then the photoresist is developed to uncover selected areas of the substrate.
Inventors
- 👤 Edward Curtis Douglas
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:14
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/70; G03F7/70216; G03F7/70358; G02; G02B; G02B27/00; G02B27/42; G02B27/4205; G03B; G03B27/00; G03B27/02; G03B27/14; G03B27/16; G03F7/20; G03F7/2002; G03F7/201
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
233 words
A method of projection printing, comprising: positioning a substantially flat substrate surface covered with a layer of photoresist in a parallel, spaced, fixed relationship to a substantially flat photomask to form a photomask assembly; exposing said photoresist layer to a diffraction image of said photomask by the projection of substantially monochromatic, collimated light through said photomask incident on said layer, said diffraction image comprising a primary image corresponding to the pattern of said photomask and a spurious diffractionassociated secondary image, and then developing said exposed photoresist layer to uncover selected areas of said substrate surface, wherein the improvement comprises: projecting said light with an oblique orientation to the plane of said photomask during said exposing, said oblique orientation being determined by an oblique angle between the direction of collimation of said light and an orthogonal line to said photomask, and by a rotational angle between a fixed reference line in the plane of said photomask and a projection of the direction of said light intersecting said fixed line in said plane of said photomask, and then varying said orientation of said light during said exposing to selectively prevent said secondary image from resulting in the uncovering of corresponding areas of said substrate surface after said developing, said exposing being for a time period by which said primary image does result in the uncovering of corresponding areas of said substrate surface after said developing.
Claim 2
Independent Claim
233 words
A method of projection printing, comprising: positioning a substantially flat substrate surface covered with a layer of photoresist in a parallel, spaced, fixed relationship to a substantially flat photomask to form a photomask assembly; exposing said photoresist layer to a diffraction image of said photomask by the projection of substantially monochromatic, collimated light through said photomask incident on said layer, said diffraction image comprising a primary image corresponding to the pattern of said photomask and a spurious diffractionassociated secondary image, and then developing said exposed photoresist layer to uncover selected areas of said substrate surface, wherein the improvement comprises: projecting said light with an oblique orientation to the plane of said photomask during said exposing, said oblique orientation being determined by an oblique angle between the direction of collimation of said light and an orthogonal line to said photomask, and by a rotational angle between a fixed reference line in the plane of said photomask and a projection of the direction of said light intersecting said fixed line in said plane of said photomask, and then varying said orientation of said light during said exposing to selectively prevent said secondary image from resulting in the uncovering of corresponding areas of said substrate surface after said developing, said exposing being for a time period by which said primary image does result in the uncovering of corresponding areas of said substrate surface after said developing.
Claim 3
Dependent Claim
16 words
The method defined in claim 1 wherein said primary diffraction image is a Fresnel diffraction image.
Claim 4
Dependent Claim
19 words
The method defined in claim 2 wherein said varying said orientation comprises varying said oblique angle of said light.
Claim 5
Dependent Claim
19 words
The method defined in claim 2 wherein said varying said orientation comprises varying said rotational angle of said light.
Claim 6
Dependent Claim
25 words
The method defined in claim 4 wherein said rotational angle is varied by rotation of said photomask assembly about an axis orthogonal to said photomask.
Claim 7
Dependent Claim
28 words
The method defined in claim 5 wherein said photoresist covered surface is positioned with a spacing of from about 6 microns to about 180 microns from said photomask.
Claim 8
Dependent Claim
26 words
The method defined in claim 6 wherein said oblique angle is fixed at about 0.01 to about 0.001 radians during said varying of said rotational angle.
Claim 9
Dependent Claim
30 words
The method defined in claim 7 wherein said light has a coherence length of at least about 300 microns and a wavelength of about 400 nanometers to about 500 nanometers.
Claim 10
Dependent Claim
14 words
The method defined in claim 1 wherein said primary image is a diffraction self-image.
Claim 11
Dependent Claim
20 words
The method defined in claim 9 wherein said varying of said orientation comprises varying said oblique angle of said light.
Claim 12
Dependent Claim
20 words
The method defined in claim 9 wherein said varying of said orientation comprises varying said rotational angle of said light.
Claim 13
Dependent Claim
23 words
The method defined in claim 11 wherein said varying of said rotational angle is by rotation of said photomask assembly about an axis.
Claim 14
Dependent Claim
28 words
The method defined in claim 11 wherein said photoresist covered surface is positioned with a spacing of from about 6 microns to about 180 microns from said photomask.
Claim 15
Dependent Claim
26 words
The method defined in claim 13 wherein said oblique angle is fixed at about 0.01 to about 0.001 radians during said varying of said rotational angle.
Claim 16
Dependent Claim
31 words
The method defined in claim 14 wherein said light has a coherence length of at least about 300 microns and a wavelength of between about 400 nanometers to about 500 nanometers.
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) | 1975-10-10 | 1976-04-10 | 1976-10-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-10-10 | 1980-04-10 | 1980-10-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-10-10 | 1984-04-10 | 1984-10-10 | $7700.00 | Window Closed / Lapsed |