US5561073A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of fabricating an isolation trench for analog bipolar devices in harsh environments
Assignee: Frontgrade Colorado Springs LLC
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Filing: 1994-04-12
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Granted: 1996-10-01
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Expires: 2014-04-12
Abstract
Abstract The present invention teaches a method of making an isolation trench. First, a silicon on insulator ("SOI") structure is provided having a conductive layer superjacent the insulator of the SOI. Second, a trench is formed down to the insulator of the SOI, thereby creating a first and second conductive region. Third, a first silicon dioxide layer is formed conformally with the sidewalls of the first and second conductive region. Fourth, a second silicon dioxide layer is formed conformally and superjacent the first silicon dioxide layer. Fifth, the remaining areas unfilled in the trench are filled with an undoped polysilicon filling. Sixth, the polysilicon layer is planarized. Seventh, an oxide cap is formed on top of the polysilicon refill. Eight, an isolation mask is formed, and the active area openings within the structure are etched down to the single crystal silicon.
Inventors
- 👤 Rick C. Jerome
- 👤 Ian R. C. Post
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 22:22
CPC Classifications
H; H10; H10D; H10D10/00; H10D10/01; H10D10/041; H10D84/00; H10D84/60; H10D84/645; H10D84/67; H10W; H10W10/00; H10W10/01; H10W10/011; H10W10/014; H10W10/0145; H10W10/0147; H10W10/10; H10W10/17
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
126 words
A method of making an isolation trench in a silicon on insulator ("SQI") substrate having an exposed dielectric layer, comprising the steps of: forming a conductive layer superjacent the dielectric layer of the SOI substrate; forming a trench through said conductive layer to expose a portion of the SOI dielectric layer, said trench having first and second sidewalls which separate said conductive layer into first and second conductive regions; forming a first silicon dioxide layer conformally over said first and second sidewalls and over said exposed portion of the SOI dielectric layer; refilling said trench with a refill comprising at least one of borophosphosilicate glass ("BPSG"), undoped silicon dioxide and tetraorthoethyloxide ("TEOS"); and reflowing said refill to improve the planarity of said refill over said trench.
Claim 2
Independent Claim
126 words
A method of making an isolation trench in a silicon on insulator ("SQI") substrate having an exposed dielectric layer, comprising the steps of: forming a conductive layer superjacent the dielectric layer of the SOI substrate; forming a trench through said conductive layer to expose a portion of the SOI dielectric layer, said trench having first and second sidewalls which separate said conductive layer into first and second conductive regions; forming a first silicon dioxide layer conformally over said first and second sidewalls and over said exposed portion of the SOI dielectric layer; refilling said trench with a refill comprising at least one of borophosphosilicate glass ("BPSG"), undoped silicon dioxide and tetraorthoethyloxide ("TEOS"); and reflowing said refill to improve the planarity of said refill over said trench.
Claim 3
Dependent Claim
28 words
The method of claim 1, wherein said step of reflowing comprises the step of: heating said refill at a temperature of approximately 850° C. for approximately 30 minutes.
Claim 4
Dependent Claim
23 words
The method of claim 1, further comprising the step of: forming a second silicon dioxide layer conformally over said first silicon dioxide layer.
Claim 5
Dependent Claim
25 words
The method of claim 3, wherein said second silicon dioxide layer formed comprises a thickness substantially in the range of 3000 Å and 8000 Å.
Claim 6
Independent Claim
202 words
A method of fabricating an isolation trench in a silicon on insulator ("SOI") substrate having an exposed dielectric layer, comprising the steps of: forming a conductive layer superjacent the dielectric layer of the SOI substrate, said conductive layer having an exposed major surface; forming a trench through said conductive layer to expose a portion of the SOI dielectric layer, said trench having first and second sidewalls which separate said conductive layer into first and second conductive regions; forming a first silicon dioxide layer conformally over said first and second sidewalls and over said exposed portion of the dielectric layer; forming a second silicon dioxide layer conformally over said first silicon dioxide layer; refilling said trench with a planarized non-conductive material; stripping one portion of said first and said second silicon dioxide layers to expose a crown of said refilled trench and to expose another portion of said first and said second silicon dioxide layers in proximity to said crown; forming a silicon dioxide pad superjacent said exposed crown and said exposed portions of said first and said second silicon dioxide layers, forming polysilicon deposits superjacent a portion of said silicon dioxide pad; and forming a silicon dioxide cover superjacent said refilled trench.
Claim 7
Independent Claim
202 words
A method of fabricating an isolation trench in a silicon on insulator ("SOI") substrate having an exposed dielectric layer, comprising the steps of: forming a conductive layer superjacent the dielectric layer of the SOI substrate, said conductive layer having an exposed major surface; forming a trench through said conductive layer to expose a portion of the SOI dielectric layer, said trench having first and second sidewalls which separate said conductive layer into first and second conductive regions; forming a first silicon dioxide layer conformally over said first and second sidewalls and over said exposed portion of the dielectric layer; forming a second silicon dioxide layer conformally over said first silicon dioxide layer; refilling said trench with a planarized non-conductive material; stripping one portion of said first and said second silicon dioxide layers to expose a crown of said refilled trench and to expose another portion of said first and said second silicon dioxide layers in proximity to said crown; forming a silicon dioxide pad superjacent said exposed crown and said exposed portions of said first and said second silicon dioxide layers, forming polysilicon deposits superjacent a portion of said silicon dioxide pad; and forming a silicon dioxide cover superjacent said refilled trench.
Claim 8
Dependent Claim
40 words
The method of claim 5, wherein said step of forming polysilicon deposits comprises the steps of: forming a polysilicon layer superjacent said silicon dioxide pad; and removing a portion of said polysilicon layer such that said polysilicon deposits are formed.
Claim 9
Dependent Claim
27 words
The method of claim 5, wherein said step of forming said silicon dioxide cover comprises the step of: oxidizing said polysilicon deposits and said silicon dioxide pad.
Claim 10
Dependent Claim
71 words
The method of claim 7, wherein said step of oxidizing comprises the steps of: forming a silicon nitride layer superjacent said silicon dioxide pad; removing portions of said silicon nitride layer in the vicinity of said trench to form first and second silicon nitride deposits on a respective one of said first and said second conductive regions; and growing a silicon dioxide formation underneath said first and second silicon nitride deposits.
Claim 11
Dependent Claim
25 words
The method of claim 5, wherein said second silicon dioxide layer comprises at least one of borophosphosilicate glass ("BPSG"), undoped silicon dioxide, and tetraethylothrosilicate ("TEOS").
Claim 12
Dependent Claim
13 words
The method of claim 5, wherein said planarized non-conductive material comprises undoped polysilicon.
References Cited (Backward Citations)
US4663832A
Cited
US4631803A
Cited
JPS6249643A
Cited
EP0232748A1
Cited
US4810667A
Cited
US4963505A
Cited
US4835115A
Cited
US5084408A
Cited
US5196373A
Cited
US5352625A
Cited
US5376560A
Cited
US5258318A
Cited
US5270265A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-10-01 | 2000-04-01 | 2000-10-01 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-10-01 | 2004-04-01 | 2004-10-01 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-10-01 | 2008-04-01 | 2008-10-01 | $7700.00 | Window Closed / Lapsed |