US4398964A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of forming ion implants self-aligned with a cut
Assignee: Signetics Corp
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Filing: 1981-12-10
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Granted: 1983-08-16
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Expires: 2001-12-10
Abstract
Abstract A method of fabricating a thick field oxide isolation layer employs dual photoresist layers and selective ion implantation. A thick field oxide layer is grown on a silicon wafer and is covered with a negative photoresist layer followed by a thicker positive photoresist layer. The positive photoresist layer is exposed through a mask and developed to leave a portion remaining where an aperture in the field oxide is to be made. Boron ions are implanted into the silicon wafer through the layers not covered by positive photoresist. The remaining positive photoresist and the underlying negative photoresist are removed to expose the field oxide, after which the patterned negative photoresist is used as a mask to etch a hole in the field oxide that is self-aligned between the boron implants.
Inventors
- 👤 Manohar L. Malwah
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:11
CPC Classifications
H; H10; H10D; H10D62/00; H10D62/10; H10D62/102; H10D62/112; H10P; H10P30/00; H10P30/20; H10P30/22; H10P76/00; H10P76/20; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/019; H10W10/10
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
211 words
A method of implanting impurity ions in regions lying laterally spaced apart within a first stratum of a semiconductor body and offset and self-aligned with the edges of an opening formed within a second stratum of material lying above said first stratum, said method comprising: (a) providing a semiconductor body having a first stratum therein and providing a second stratum of material adjacent to said first stratum, (b) superimposing successive layers of a thin negative photoresist and a thicker positive photoresist over said second stratum in that order, (c) removing only selected spaced portions of said positive photoresist layer by photolithographic means to produce voids therein, (d) subjecting the structure thus formed to impurity ions of such velocity that impurity ions deposit in laterally spaced implanted regions of said first stratum that are aligned with said voids but are blocked from regions underlying said positive photoresist layer, (e) removing the remaining positive photoresist layer and the underlying part of negative photoresist layer, and (f) while using the remaining negative photoresist layer as a mask, removing material of said second stratum that is uncovered by said negative photoresist layer to produce an opening within said second stratum that is self-aligned with and disposed between said laterally spaced regions of implanted impurity ions.
Claim 2
Independent Claim
211 words
A method of implanting impurity ions in regions lying laterally spaced apart within a first stratum of a semiconductor body and offset and self-aligned with the edges of an opening formed within a second stratum of material lying above said first stratum, said method comprising: (a) providing a semiconductor body having a first stratum therein and providing a second stratum of material adjacent to said first stratum, (b) superimposing successive layers of a thin negative photoresist and a thicker positive photoresist over said second stratum in that order, (c) removing only selected spaced portions of said positive photoresist layer by photolithographic means to produce voids therein, (d) subjecting the structure thus formed to impurity ions of such velocity that impurity ions deposit in laterally spaced implanted regions of said first stratum that are aligned with said voids but are blocked from regions underlying said positive photoresist layer, (e) removing the remaining positive photoresist layer and the underlying part of negative photoresist layer, and (f) while using the remaining negative photoresist layer as a mask, removing material of said second stratum that is uncovered by said negative photoresist layer to produce an opening within said second stratum that is self-aligned with and disposed between said laterally spaced regions of implanted impurity ions.
Claim 3
Dependent Claim
21 words
The invention according to claim 1, wherein said semiconductor body and said second stratum of material are made of different material.
Claim 4
Dependent Claim
28 words
The invention according to claim 1, wherein said semiconductor body is silicon and said second stratum of material comprises silicon dioxide that is thermally grown on said silicon.
Claim 5
Dependent Claim
15 words
The invention according to claim 1, wherein said second stratum of material comprises silicon nitride.
Claim 6
Dependent Claim
16 words
The invention according to claim 3 wherein said silicon dioxide layer is about 4000-6000 angstroms thick.
Claim 7
Dependent Claim
25 words
The invention according to claim 5 wherein said negative photoresist layer is about 3000 angstroms thick and said positive photoresist is about 15,000 angstroms thick.
Claim 8
Dependent Claim
20 words
The invention according to claim 1, wherein said semiconductor body comprises P type silicon and said impurity ions comprise boron.
Claim 9
Dependent Claim
35 words
The invention according to claim 1, wherein in step (e) said positive photoresist layer is removed by chemical stripping, after which said underlying part of the negative photoresist layer is removed with a developer solvent.
Claim 10
Dependent Claim
21 words
The invention according to claim 1, wherein in step (f) the material of said second stratum is removed by chemical means.
Claim 11
Dependent Claim
23 words
The invention according to claim 1, and further including the step of removing the remaining negative photoresist layer after said opening is produced.
Claim 12
Dependent Claim
17 words
The invention according to claim 10, wherein said remaining negative photoresist layer is removed by chemical stripping.
References Cited (Backward Citations)
US4004044A
Cited
US4022932A
Cited
US4040891A
Cited
US4201800A
Cited
US4144101A
Cited
US4253888A
Cited
US4311533A
Cited
US4350541A
Cited
US4231811A
Cited
US4341571A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-08-15 | 1987-02-14 | 1987-08-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-08-15 | 1991-02-14 | 1991-08-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-08-15 | 1995-02-14 | 1995-08-16 | $7700.00 | Window Closed / Lapsed |