US4022927A
Expired / Lapsed
US
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Methods for forming thick self-supporting masks
Assignee: International Business Machines Corp
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Filing: 1975-06-30
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Granted: 1977-05-10
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Expires: 1995-06-30
Abstract
Abstract A method of constructing a relatively thick, self-supporting mask suitable for electron beam projection processes. Thickness is achieved by multiple steps of coating with resist, exposure and development. Either positive or negative resist may be used for second and subsequent coatings. Second and subsequent exposures are directed through the first relatively thin mask formed and through the substrate to eliminate critical alignment of subsequent masks. When desired thickness is achieved an even thicker frame may be fabricated for support purposes and the mask may then be lifted off the substrate on which it had rested during the fabrication steps. When positive resist is employed, the resist remaining after development is baked on to give added structural strength to the mask. This baked resist can be coated with an additional layer of metal by evaporation or sputtering to give greater mechanical strength. When negative resist is employed, the portions of the resist protected by the relatively thin previously formed mask are removed and additional material is plated to increase the thickness and strength of the mask. The unprotected resist material is then also removed. The completed mask can be further strengthened by evaporating or sputtering an additional layer of metal or oxide.
Inventors
- 👤 Aloysius T. Pfeiffer
- 👤 Lubomyr T. Romankiw
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 22:05
CPC Classifications
G; G03; G03F; G03F1/00; G03F1/20; Y; Y10; Y10S; Y10S430/00; Y10S430/143; Y10S430/153; Y10S430/167; Y10S430/168
Claims Analysis
Total Claims: 46
Claim 1
Independent Claim
137 words
A method of fabricating a self-supporting mask with aspect ratio> 1 for increasing the strength of said mask and making it capable of being self-supported in which a relatively thin mask is supported on a substrate with an easily selectively removable layer lying between said substrate and said mask, both said layer and said substrate being transparent to selected radiation, said method including the steps of: coating, to a desired thickness, the exposed surface of said mask with a material sensitive to said radiation, exposing said mask to said selected radiation with said mask located with the substrate lying between said selected radiation and said material, developing said material to remove selected areas of said material, and removing said easily selectively removable layer to lift said mask from said substrate thereby providing a self-supporting relatively thick mask.
Claim 2
Independent Claim
137 words
A method of fabricating a self-supporting mask with aspect ratio> 1 for increasing the strength of said mask and making it capable of being self-supported in which a relatively thin mask is supported on a substrate with an easily selectively removable layer lying between said substrate and said mask, both said layer and said substrate being transparent to selected radiation, said method including the steps of: coating, to a desired thickness, the exposed surface of said mask with a material sensitive to said radiation, exposing said mask to said selected radiation with said mask located with the substrate lying between said selected radiation and said material, developing said material to remove selected areas of said material, and removing said easily selectively removable layer to lift said mask from said substrate thereby providing a self-supporting relatively thick mask.
Claim 3
Dependent Claim
21 words
The method of claim 1 in which said material coated on the exposed surface of said mask comprises a positive resist.
Claim 4
Dependent Claim
44 words
The method of claim 2 which further includes a step of baking, subsequent to said developing step in which the temperature of said material is increased sufficient to destroy sensitizer of said resist followed by a step of cooling said material to ambient temperature.
Claim 5
Dependent Claim
35 words
The method of claim 2 in which the temperature of said material is increased to at least 110° C, subsequent to said developing step, followed by a step of cooling said material to ambient temperature.
Claim 6
Dependent Claim
19 words
The method of claim 4 in which the temperature of said material is increased in a plurality of stages.
Claim 7
Dependent Claim
31 words
The method of claim 2 wherein said steps of coating, exposing and developing are carried out a plurality of times prior to said step of removing said easily selectively removable layer.
Claim 8
Dependent Claim
22 words
The method of claim 2 in which the desired thickness of said coating step is less than or equal to 15 microns.
Claim 9
Dependent Claim
33 words
The method of claim 2 wherein said step of coating is carried out in two operations, said first operation employing a relatively dilute resist and said second operation employing a relatively viscous resist.
Claim 10
Dependent Claim
15 words
The method of claim 8 in which each of said coating steps comprises spin coating.
Claim 11
Dependent Claim
12 words
The method of claim 2 wherein said selected radiation comprises ultraviolet light.
Claim 12
Dependent Claim
16 words
The method of claim 2 wherein said removing step comprises chemical etching of said intermediate layer.
Claim 13
Dependent Claim
26 words
The method of claim 1 which includes a step of electroforming a thick support frame subsequent to said developing step and prior to said removing step.
Claim 14
Dependent Claim
31 words
The method of claim 1 which includes a further step of strengthening said mask by depositing, by evaporation or sputtering, onto said mask additional non-magnetic material subsequent to said removing step.
Claim 15
Dependent Claim
11 words
The method of claim 3 in which said material comprises PMMA.
Claim 16
Dependent Claim
21 words
The method of claim 3 in which said baking step is carried out at a temperature of at least 135° C.
Claim 17
Dependent Claim
21 words
The method of claim 16 in which said baking step is carried out at a temperature of at least 110° C.
Claim 18
Dependent Claim
13 words
The method of claim 2 in which said selected radiation comprises X-ray radiation.
Claim 19
Dependent Claim
20 words
The method of claim 17 in which said baking is carried out at a temperature as high as 250° C.
Claim 20
Dependent Claim
12 words
The method of claim 1 wherein said material comprises a negative resist.
Claim 21
Dependent Claim
20 words
The method of claim 19 which further includes a step of plating metal into areas vacated during said developing step.
Claim 22
Dependent Claim
22 words
The method of claim 20 in which said steps of coating, exposing, developing and plating are carried out a plurality of times.
Claim 23
Dependent Claim
21 words
The method of claim 19 wherein said desired thickness of said coating step is less than or equal to 15 microns.
Claim 24
Dependent Claim
35 words
The method of claim 20 in which said coating step comprises at least two coatings steps, the first of which employs a relatively dilute negative resist, and the second employs a relatively viscous negative resist.
Claim 25
Dependent Claim
13 words
The method of claim 19 in which said selected radiation comprises ultraviolet light.
Claim 26
Dependent Claim
13 words
The method of claim 19 in which said selected radiation comprises X-ray radiation.
Claim 27
Dependent Claim
17 words
The method of claim 19 in which said removing step comprises chemical etching of said intermediate layer.
Claim 28
Dependent Claim
15 words
The method of claim 23 in which each of said coating steps comprises spin coating.
Claim 29
Independent Claim
222 words
The method of fabricating a mask for electron beam projection processing which is self-supporting comprises the sequential steps of: a. coating a substrate transparent to a first radiation with an easily selectively removable layer selected from the group of Cu, Ti, Au, Cr, Ta, Hf, Sb and Zn or mixtures thereof; b. coating the product of step (a) with a plating base metal selected from the group of Cu, Au, Ag, Zn, Pd and Pt; c. coating the product of step (b) with a resist sensitive to a second radiation; d. exposing the product of step (c) to said second radiation which passes through a mask containing a desired pattern; e. developing said resist, plating metal into areas defined by said developed resist and removing any remaining resist; f. removing exposed portions of the layer deposited in step (b); g. removing exposed portions of the layer deposited in step (a); h. coating the product of step (g) with a second resist sensitive to said first radiation; i. exposing said second resist to said first radiation which first radiation first passes through said substrate, said second resist being exposed to said first radiation which is not blocked by the metal deposited in step (e); j. developing said second resist; and, k. removing said removable layer to thereby lift the mask from said substrate.
Claim 30
Independent Claim
222 words
The method of fabricating a mask for electron beam projection processing which is self-supporting comprises the sequential steps of: a. coating a substrate transparent to a first radiation with an easily selectively removable layer selected from the group of Cu, Ti, Au, Cr, Ta, Hf, Sb and Zn or mixtures thereof; b. coating the product of step (a) with a plating base metal selected from the group of Cu, Au, Ag, Zn, Pd and Pt; c. coating the product of step (b) with a resist sensitive to a second radiation; d. exposing the product of step (c) to said second radiation which passes through a mask containing a desired pattern; e. developing said resist, plating metal into areas defined by said developed resist and removing any remaining resist; f. removing exposed portions of the layer deposited in step (b); g. removing exposed portions of the layer deposited in step (a); h. coating the product of step (g) with a second resist sensitive to said first radiation; i. exposing said second resist to said first radiation which first radiation first passes through said substrate, said second resist being exposed to said first radiation which is not blocked by the metal deposited in step (e); j. developing said second resist; and, k. removing said removable layer to thereby lift the mask from said substrate.
Claim 31
Dependent Claim
43 words
The method of claim 28 in which said second resist is a positive resist and which furher includes a step of baking said developed second resist at a temperature of at least 110° C subsequent to step (j) and prior to step (k).
Claim 32
Dependent Claim
15 words
The method of claim 29 in which said baking temperature is at least 135° C.
Claim 33
Dependent Claim
42 words
The method of claim 28 in which said resist is a positive resist and which includes the further step of baking said developed second resist at a temperature as high as 250° C subsequent to step (j) and prior to step (k).
Claim 34
Dependent Claim
28 words
The method of claim 29 wherein said coating step (h), said exposing step (i), said developing step (j) and said baking step are performed a plurality of times.
Claim 35
Dependent Claim
13 words
The method of claim 28 in which said first radiation comprises ultraviolet light.
Claim 36
Dependent Claim
17 words
The method of claim 33 in which said ultraviolet light has a wavelength of about 3,500 A.
Claim 37
Dependent Claim
19 words
The method of claim 33 in which said ultraviolet light has a wavelength on the order of 2,000 A.
Claim 38
Dependent Claim
14 words
The method of claim 28 in which said second resist comprises a negative resist.
Claim 39
Dependent Claim
32 words
The method of claim 36 which includes a further step of plating additional metal, subsequent to step (j) into the areas from which said second resist was removed in said step (j).
Claim 40
Dependent Claim
30 words
The method of claim 37 in which said coating step (h), said exposing step (i), said developing said (j), and further plating step are carried out a plurality of times.
Claim 41
Dependent Claim
13 words
The method of claim 36 in which said removing step comprises chemical etching.
Claim 42
Dependent Claim
37 words
The method of claim 28 in which said step (h) comprises a plurality of coating steps, an initial coating step employing a relatively dilute second resist and said subsequent coating step employing a relatively viscous second resist.
Claim 43
Dependent Claim
22 words
The method of claim 40 in which each of said plurality of coating steps included in said step (h) includes spin coating.
Claim 44
Dependent Claim
13 words
The method of claim 29 in which said first radiation comprises X-ray radiation.
Claim 45
Dependent Claim
22 words
The method of claim 28 which includes the further sequential step of depositing, by evaporation or sputtering, an additional non-magnetic material layer.
Claim 46
Dependent Claim
26 words
The method of claim 43 in which said additional non-magnetic material is selected from the group of Cu, Au, Ti, Cr and Ta or combinations thereof.
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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) | 1980-05-09 | 1980-11-08 | 1981-05-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-09 | 1984-11-08 | 1985-05-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-09 | 1988-11-08 | 1989-05-10 | $7700.00 | Window Closed / Lapsed |