US3734787A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fabrication of diffused junction capacitor by simultaneous outdiffusion
Assignee: International Business Machines Corp
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Filing: 1970-01-09
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Granted: 1973-05-22
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Expires: 1990-01-09
Abstract
Abstract A diffused junction capacitor having two P N junctions, one in the semiconductor substrate and one in an epitaxial layer thereon and exhibiting high capacitance per unit area. A method for forming such a capacitor makes use of the fact that the outdiffusion rate for boron is much faster than the outdiffusion rate for arsenic, whereby, for instance, boron and arsenic diffused into the surface of a semiconductor wafer can, after the growth of an N epitaxial layer, be diffused into the N epitaxial layer. Since the boron outdiffuses much faster, it will cover a larger area than the arsenic outdiffusion. This will, in turn, result in two P -N junctions, one in the substrate and one in the N epitaxial layer.
Inventors
- 👤 V Dhaka
- 👤 W Krolikowski
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:47
CPC Classifications
H; H10; H10D; H10D84/00; H10D84/01; H10D1/00; H10D1/60; H10D1/62; H10D1/64; Y; Y10; Y10S; Y10S148/00; Y10S148/037; Y10S148/085; Y10S148/151; Y10S438/00; Y10S438/901
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
20 words
The process of claim 1 wherein said outdiffusion occurs simultaneously with the growth of said epitaxial layer upon said substrate.
Claim 2
Dependent Claim
27 words
The process of claim 1 wherein said P impurity has a rate of diffusion greater than said N impurity by a factor of at least about 10.
Claim 3
Dependent Claim
63 words
The process of claim 1 wherein said N diffused zone is formed in said semiconductor substrate to a depth of about 1 to about 2 microns, and said P diffused zone is formed in said substrate to a depth within the range of about 1 to about 2 microns, said P diffused zone being deeper in said substrate than said N diffused zone.
Claim 4
Dependent Claim
25 words
The process of claim 4 wherein said outdiffusion is performed into said epitaxy layer to a depth of from about 1 to about 1.5 microns.
Claim 5
Dependent Claim
20 words
The process of claim 1 wherein the said P diffused zone is formed prior to forming said N diffused zone.
Claim 6
Dependent Claim
27 words
The process of claim 1 wherein the said separate electrical contact to said P zone and said N zone are made by diffusion reach-throughs in said substrate.
Claim 7
Dependent Claim
165 words
A procEss of forming a self-isolated double diffused junction capacitor comprising: forming a N diffused zone in a P type semiconductor substrate, said diffused zone having a major surface at the surface of the semiconductor substrate and also having side surfaces within said substrate substantially perpendicular to said major surface; forming a P diffused zone in said substrate overlapping the entire side surfaces and a portion of said major surface of said N diffused zone in said substrate and to a depth greater than said N zone, the surface concentration of said P impurity being less than the concentration of said N impurity; growing an epitaxial layer on said substrate; outdiffusing said N and said P impurity into said epitaxial layer, said P impurity having a greater diffusion constant than said N impurity whereby a P N junction is formed in said substrate and in said epitaxial layer; and making separate electrical contact to said P zone and said N zone to form said capacitor.
Claim 8
Dependent Claim
21 words
The process of claim 8 wherein said N diffused zone contains arsenic dopant and said P diffused zone contains boron dopant.
Claim 9
Dependent Claim
20 words
The process of claim 8 wherein the said P diffused zone is formed prior to forming said N diffused zone.
References Cited (Backward Citations)
US3260902A
Cited
US3449643A
Cited
FR1541490A
Cited
US3474308A
Cited
US3474309A
Cited
US3502951A
Cited
US3617827A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-05-21 | 1976-11-20 | 1977-05-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-21 | 1980-11-20 | 1981-05-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-21 | 1984-11-20 | 1985-05-22 | $7700.00 | Window Closed / Lapsed |