US4810667A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Dielectric isolation using isolated silicon by limited anodization of an N+ epitaxially defined sublayer in the presence of a diffusion under film layer
Assignee: Texas Instruments Inc
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Filing: 1987-04-28
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Granted: 1989-03-07
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Expires: 2007-04-28
Abstract
Abstract The disclosure relates to a method of forming an isolated semiconductor, preferably of the vertical bipolar variety, wherein a porous highly doped semiconductor layer is oxidized and, with a trench containing silicon oxide therein, forms a region encasing a moderately doped epitaxial layer disposed beneath a lightly doped epitaxial layer. The vertical bipolar device is formed in the moderately doped and lightly doped layers with the highly doped epitaxially deposited layer, which is now a silicon oxide layer, forming a portion of the isolation. The anodization of the highly doped layer takes place using an anodizing acid at a temperature of from about 0 to about 10 degrees C.
Inventors
- 👤 Eldon J. Zorinsky
- 👤 David B. Spratt
- 👤 Richard L. Yeakley
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 12:44
CPC Classifications
H; H10; H10P; H10P90/00; H10P90/19; H10P90/1904; H10P90/1906; H10W; H10W10/00; H10W10/01; H10W10/061; H10W10/10; H10W10/181; H10P90/191; H10W10/011; H10W10/014; H10W10/17
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
148 words
A method for forming a bipolar transistor in an isolated epitaxial island on an n-type silicon substrate, comprising the steps of: (a) forming a first highly doped n-type epitaxial silicon layer on said substrate; (b) forming a second moderately doped n-type epitaxial silicon layer on said highly doped epitaxial silicon layer; (c) forming a third lightly doped n-type epitaxial silicon layer on said moderately doped epitaxial silicon layer; (d) forming a trench extending through each of said first, second and third layers and into said substrate; (e) exposing said substrate to an anodizing agent maintained at a temperature from about 0 to about 10 degrees C and a voltage whereby porous silicon is selectively formed only in the said first highly doped layer; (f) oxidizing the porous silicon to form silicon dioxide in the porous layer; and (g) forming a semiconductor device in said second and third layers.
Claim 2
Independent Claim
148 words
A method for forming a bipolar transistor in an isolated epitaxial island on an n-type silicon substrate, comprising the steps of: (a) forming a first highly doped n-type epitaxial silicon layer on said substrate; (b) forming a second moderately doped n-type epitaxial silicon layer on said highly doped epitaxial silicon layer; (c) forming a third lightly doped n-type epitaxial silicon layer on said moderately doped epitaxial silicon layer; (d) forming a trench extending through each of said first, second and third layers and into said substrate; (e) exposing said substrate to an anodizing agent maintained at a temperature from about 0 to about 10 degrees C and a voltage whereby porous silicon is selectively formed only in the said first highly doped layer; (f) oxidizing the porous silicon to form silicon dioxide in the porous layer; and (g) forming a semiconductor device in said second and third layers.
Claim 3
Dependent Claim
17 words
The method of claim 1 further including the step of forming a sidewall oxide in said trench.
Claim 4
Dependent Claim
16 words
The method of claim 1 further including the step of filling said trench with silicon oxide.
Claim 5
Dependent Claim
16 words
The method of claim 2 further including the step of filling said trench with silicon oxide.
Claim 6
Dependent Claim
42 words
The method of claim 1 further including forming an oxide layer over said substrate prior to step (g); forming a collector contact region in said first layer extending to said second layer and forming base and emitter regions in said first layer.
Claim 7
Dependent Claim
42 words
The method of claim 2 further including forming an oxide layer over said substrate prior to step (g); forming a collector contact region in said first layer extending to said second layer and forming base and emitter regions in said first layer.
Claim 8
Dependent Claim
42 words
The method of claim 3 further including forming an oxide layer over said substrate prior to step (g); forming a collector contact region in said first layer extending to said second layer and forming base and emitter regions in said first layer.
Claim 9
Dependent Claim
42 words
The method of claim 4 further including forming an oxide layer over said substrate prior to step (g); forming a collector contact region in said first layer extending to said second layer and forming base and emitter regions in said first layer.
Claim 10
Dependent Claim
18 words
The method of claim 1 wherein said highly doped N-type layer has a thickness of about 0.5 microns.
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) | 1992-03-06 | 1992-09-05 | 1993-03-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-03-06 | 1996-09-05 | 1997-03-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-03-06 | 2000-09-05 | 2001-03-07 | $7700.00 | Window Closed / Lapsed |