US4261791A
Expired / Lapsed
US
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Two step method of cleaning silicon wafers
Assignee: RCA Corp
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Filing: 1979-09-25
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Granted: 1981-04-14
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Expires: 1999-09-25
Abstract
Abstract Silicon wafers are cleaned by first immersing them in a film forming solution which reacts with the dirty wafers to form a film on the wafers and then immersing the wafers in a film stripping solution which removes the film. For silicon wafers both the film forming solution and the film stripping solution may be formed from separate aqueous source solutions comprising 49% HF by weight and 70% HNO 3 by weight, respectively. The film forming solution comprises 99.1% to 99.5% by volume the HF solution and 0.5% to 0.9% by volume the HNO 3 solution. A small quantity of a wetting agent may be present in this solution. The stripping solution comprises 95% to 99% by volume of the HNO 3 solution and 5% to 1% by volume of the HF solution. When utilized at room temperature the film forming solution forms a film on the wafers and the stripping solution removes the film with a minimum of attack on the silicon of the main wafer body. This silicon wafer cleaning method is successful with all silicon wafers independent of doping level.
Inventors
- 👤 Stanley Shwartzman
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 14:54
CPC Classifications
H; H10; H10P; H10P70/00; H10P70/10; H10P70/15; Y; Y10; Y10S; Y10S134/00; Y10S134/902
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
83 words
A method of cleaning a dirty silicon semiconductor wafer comprising: intentionally exposing the wafer to an environment which reacts with the wafer to form a dirt removing film on the wafer, said environment being a film forming solution initially comprising effectively: 99.1%-99.5% by volume of an aqueous source solution of 49% by weight HF; and 0.5%-0.9% by volume of an aqueous source solution of 70% by weight HNO 3 ; and subsequently removing said film in order to leave a clean wafer surface.
Claim 2
Independent Claim
83 words
A method of cleaning a dirty silicon semiconductor wafer comprising: intentionally exposing the wafer to an environment which reacts with the wafer to form a dirt removing film on the wafer, said environment being a film forming solution initially comprising effectively: 99.1%-99.5% by volume of an aqueous source solution of 49% by weight HF; and 0.5%-0.9% by volume of an aqueous source solution of 70% by weight HNO 3 ; and subsequently removing said film in order to leave a clean wafer surface.
Claim 3
Dependent Claim
15 words
The method recited in claim 1 wherein: said film forming solution includes a wetting agent.
Claim 4
Dependent Claim
22 words
The method recited in claim 1 wherein: said film forming solution comprises effectively 0.7%±0.05% by volume of said HNO 3 source solution.
Claim 5
Dependent Claim
43 words
The method recited in claim 1 wherein said removing step comprises: treating said wafer with a film stripping solution initially comprising effectively: 80%-99% by volume of said source solution of HNO 3 ; and 1%-20% by volume of said source solution of HF.
Claim 6
Dependent Claim
34 words
The method recited in claim 4 wherein said stripping solution initially comprises effectively: 95%-99% by volume of said source solution of HNO 3 ; and 1%-5% by volume of said source solution of HF.
Claim 7
Dependent Claim
36 words
The method recited in claim 5 wherein said stripping solution initially comprises effectively: substantially 95% by volume of said source solution of HNO 3 ; and substantially 5% by volume of said source solution of HF.
Claim 8
Independent Claim
120 words
A method of cleaning a dirty silicon semiconductor wafer comprising: intentionally exposing the wafer to an environment which reacts with the wafer to form a dirt removing film on the wafer, said environment being a film forming solution initially comprising effectively: 99.1%-99.5% by volume of an aqueous source solution of 49% by weight HF; and 0.5%-0.9% by volume of an aqueous source solution by 70% by weight HNO 3 ; and subsequently removing said film in order to leave a clean wafer surface, said removing being accomplished by treating said wafer with a film stripping solution initially comprising effectively: 95%-99% by volume of said source solution of HNO 3 ; and 1%-5% by volume of said source solution of HF.
Claim 9
Independent Claim
120 words
A method of cleaning a dirty silicon semiconductor wafer comprising: intentionally exposing the wafer to an environment which reacts with the wafer to form a dirt removing film on the wafer, said environment being a film forming solution initially comprising effectively: 99.1%-99.5% by volume of an aqueous source solution of 49% by weight HF; and 0.5%-0.9% by volume of an aqueous source solution by 70% by weight HNO 3 ; and subsequently removing said film in order to leave a clean wafer surface, said removing being accomplished by treating said wafer with a film stripping solution initially comprising effectively: 95%-99% by volume of said source solution of HNO 3 ; and 1%-5% by volume of said source solution of HF.
Claim 10
Dependent Claim
21 words
The method recited in claim 7 wherein: said film forming solution comprises 0.7%±0.5% by volume of said HNO 3 source solution.
Claim 11
Dependent Claim
28 words
The method recited in claim 5 wherein: said exposing is for a period of about one minute; and said treating is for a period of about one minute.
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) | 1984-04-13 | 1984-10-13 | 1985-04-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-04-13 | 1988-10-13 | 1989-04-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-04-13 | 1992-10-13 | 1993-04-14 | $7700.00 | Window Closed / Lapsed |