US4050967A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of selective aluminum diffusion
Assignee: RCA Corp
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Filing: 1976-12-09
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Granted: 1977-09-27
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Expires: 1996-12-09
Abstract
Abstract A silicon substrate is coated with a mask comprised of the combination of a silicon dioxide layer and a layer of undoped polycrystalline silicon. Aluminum is then diffused through windows formed in the mask. The mask has proven effective for relatively deep aluminum diffusion.
Inventors
- 👤 Wojciech Rosnowski
- 👤 Samuel Ponczak
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 17:28
CPC Classifications
H; H10; H10P; H10P76/00; H10P76/40; H10P32/00; H10P32/10; H10P32/12; H10P32/17; H10P32/171; Y; Y10; Y10S; Y10S148/00; Y10S148/033; Y10S148/122
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
93 words
A method of selectively diffusing aluminum into a wafer including a silicon body having a surface comprising: forming a masking layer comprising a layer of silicon dioxide and a layer of polycrystalline silicon on a surface of said body; forming an opening in at least one of said layers thereby defining a masked portion and an unmasked portion of said surface; subjecting said wafer, including both the unmasked portion of said surface and said masked portion to a source of aluminum impurities; and diffusing said aluminum through said opening and into said body.
Claim 2
Independent Claim
93 words
A method of selectively diffusing aluminum into a wafer including a silicon body having a surface comprising: forming a masking layer comprising a layer of silicon dioxide and a layer of polycrystalline silicon on a surface of said body; forming an opening in at least one of said layers thereby defining a masked portion and an unmasked portion of said surface; subjecting said wafer, including both the unmasked portion of said surface and said masked portion to a source of aluminum impurities; and diffusing said aluminum through said opening and into said body.
Claim 3
Dependent Claim
13 words
The method of claim 1, wherein said impurity source is an aluminum vapor.
Claim 4
Dependent Claim
36 words
The method of claim 2, wherein said diffusion is accomplished by: forming said aluminum vapor in a vacuum chamber; placing said body into said chamber; and heating said body to diffuse said aluminum through said opening.
Claim 5
Dependent Claim
27 words
The method of claim 1, wherein said impurity source is an aluminum layer which is formed on said undoped polycrystalline layer, and which extends through said opening.
Claim 6
Dependent Claim
14 words
The method of claim 1, wherein said layer of polycrystalline silicon is substantially undoped.
Claim 7
Dependent Claim
20 words
The method of claim 5, wherein said layer of polycrystalline silicon has a resistivity no less than 10 3 ohm-cm.
Claim 8
Dependent Claim
28 words
The method of claim 1, wherein said wafer is heated to a temperature of between 1000° C and 1200° C for a period of at least 2 hours.
Claim 9
Dependent Claim
27 words
The method of claim 1 wherein said opening is formed to said body through said layer of silicon dioxide and also through said layer of polycrystalline silicon.
Claim 10
Dependent Claim
30 words
The method of claim 1, wherein said opening is formed in said layer of silicon dioxide and wherein said layer of polycrystalline silicon extends through said opening to said substrate.
Claim 11
Dependent Claim
29 words
The method of claim 1, wherein said opening is formed in said layer of polycrystalline silicon and wherein said opening does not extend through said layer of silicon dioxide.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-09-26 | 1981-03-28 | 1981-09-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-09-26 | 1985-03-28 | 1985-09-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-09-26 | 1989-03-28 | 1989-09-27 | $7700.00 | Window Closed / Lapsed |