US4775609A
Expired / Lapsed
US
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Image reversal
Assignee: Hoechst Celanese Chemical Co
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Filing: 1987-05-18
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Granted: 1988-10-04
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Expires: 2007-05-18
Abstract
Abstract A positive acting photoresist system including a hydrophobic blocked polymer can be made to function in a negative sense (or tone) in what is known as an "image reversal" process, which may be summarized as follows: (1) After being exposed to UV radiation through a mask pattern to produce photogenerated acid, a photoresist coated wafer is treated with a gaseous base such as ammonia. The base reacts with photogenerated acid to produce a salt, effectively preventing deblocking of the polymer. (2) The wafer then is exposed to a vacuum to remove any excess base. (3) The wafer is then flood-exposed (i.e., no mask is used) with UV light. This produces acid in the previously masked-over areas. The sensitizer has already been largely destroyed in the original image area and so little acid is produced there. (4) The wafer is then baked to deblock the polymer in the area not exposed in step (1) and developed in aqueous alkali. The resulting image is the inverse of the original mask pattern. That is, those areas that received irradiation through the mask remain, and those areas that were flood-exposed are removed by the developer.
Inventors
- 👤 Michael J. McFarland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:12
CPC Classifications
G; G03; G03F; G03F7/00; G03F7/004; G03F7/039
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
161 words
A method of image reversal for positive acting photoresists which utilize a latent photoacid to photogenerate acid which during subsequent baking deblocks a hydrophobic polymer to make it soluble in aqueous alkaline developing solutions which comprises the steps of: (1) imagewise exposure of a photoresist layer comprising said blocked polymer and said latent photoacid on a substrate to photogenerate an acid without deblocking said polymer; (2) in the absence of a post-exposure baking step, treatment of the exposed layer with a gaseous base to neutralize the acid generated in step (1) to a salt via an acid-base reaction; (3) removal of excess base; (4) flood exposure of the resist layer to photogenerate acid in areas not exposed in step (1); (5) baking the exposed photoresist layer of step (4) to deblock said polymer in the area not exposed in step (1); and (6) development in aqueous alkaline developer to remove the resist layer except for the portion exposed in step (1).
Claim 2
Independent Claim
161 words
A method of image reversal for positive acting photoresists which utilize a latent photoacid to photogenerate acid which during subsequent baking deblocks a hydrophobic polymer to make it soluble in aqueous alkaline developing solutions which comprises the steps of: (1) imagewise exposure of a photoresist layer comprising said blocked polymer and said latent photoacid on a substrate to photogenerate an acid without deblocking said polymer; (2) in the absence of a post-exposure baking step, treatment of the exposed layer with a gaseous base to neutralize the acid generated in step (1) to a salt via an acid-base reaction; (3) removal of excess base; (4) flood exposure of the resist layer to photogenerate acid in areas not exposed in step (1); (5) baking the exposed photoresist layer of step (4) to deblock said polymer in the area not exposed in step (1); and (6) development in aqueous alkaline developer to remove the resist layer except for the portion exposed in step (1).
Claim 3
Dependent Claim
23 words
The method of claim 1 wherein the polymer is an imide-containing polymer where the imide functionalities have been blocked with an acid-labile group.
Claim 4
Dependent Claim
11 words
The method of claim 2 wherein the polymer is poly(N-tert-butyloxycarbonyl maleimide-co-styrene).
Claim 5
Dependent Claim
12 words
The method of claim 2 wherein the polymer is poly(N-tert-butyloxycarbonyl maleimide-co-4-tert-butyl styrene).
Claim 6
Dependent Claim
13 words
The method of claim 2 wherein the polymer is poly(N-tert-butyloxycarbonyl maleimide-co-decyl vinyl ether).
Claim 7
Dependent Claim
11 words
The method of claim 2 wherein the polymer is poly(dimethyl-N-tert-butyloxycarbonyl glutarimide).
Claim 8
Dependent Claim
11 words
The method of claim 2 wherein the polymer is poly(N-tert-butyloxycarbonyl maleimide).
Claim 9
Dependent Claim
11 words
The method of claim 2 wherein the blocking group is tert-butyloxycarbonyl.
Claim 10
Dependent Claim
11 words
The method of claim 2 wherein the blocking group is benzyloxycarbonyl.
Claim 11
Dependent Claim
24 words
The method of claim 1 wherein the polymer is a phenol containing polymer where the hydroxy functionalities have been blocked with an acid-labile group.
Claim 12
Dependent Claim
11 words
The method of claim 10 wherein the polymer is poly(tert-butyloxycarbonyloxy-α-alkyl styrene).
Claim 13
Dependent Claim
11 words
The method of claim 10 wherein the polymer is poly(tert-butyloxycarbonyloxy styrene).
Claim 14
Dependent Claim
11 words
The method of claim 10 wherein the blocking group is tert-butyloxycarbonyl.
Claim 15
Dependent Claim
11 words
The method of claim 10 wherein the blocking group is benzyloxycarbonyl.
Claim 16
Dependent Claim
25 words
The method of claim 1 wherein the polymer is a carboxylic acid containing polymer where the acid functionalities have been blocked with an acid-labile group.
Claim 17
Dependent Claim
11 words
The method of claim 15 wherein the polymer is poly(tert-butyl methacrylate).
Claim 18
Dependent Claim
11 words
The method of claim 15 wherein the polymer is poly(tert-butyl p-vinylbenzoate).
Claim 19
Dependent Claim
18 words
The method of claim 1 wherein the photogenerated acid is produced by the irradiation of an onium salt.
Claim 20
Dependent Claim
14 words
The method of claim 18 wherein the onium salt is an aryl diazonium salt.
Claim 21
Dependent Claim
13 words
The method of claim 18 wherein the onium salt is a diaryliodonium salt.
Claim 22
Dependent Claim
13 words
The method of claim 18 wherein the onium salt is a triarylsulfonium salt.
Claim 23
Dependent Claim
13 words
The method of claim 20 wherein the onium salt is a diphenyliodonium trifluoromethanesulfonate.
Claim 24
Dependent Claim
12 words
The method of claim 21 wherein the onium salt is triphenylsulfonium trifluoromethanesulfonate.
Claim 25
Dependent Claim
21 words
The method of claim 1 wherein the base is a primary, secondary or tertiary amine having 1 to 12 carbon atoms.
Claim 26
Dependent Claim
10 words
The method of claim 1 wherein the base is ammonia.
Claim 27
Dependent Claim
10 words
The method of claim 24 wherein the base is triethylamine.
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) | 1991-10-04 | 1992-04-04 | 1992-10-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-10-04 | 1996-04-04 | 1996-10-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-10-04 | 2000-04-04 | 2000-10-04 | $7700.00 | Window Closed / Lapsed |