US3920495A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of forming reflective means in a light activated semiconductor controlled rectifier
Assignee: Westinghouse Electric Corp
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Filing: 1973-08-29
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Granted: 1975-11-18
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Expires: 1993-08-29
Abstract
Abstract This disclosure is concerned with a method of forming light reflective etch pits preferably having a tetrahedral pattern, in a surface, preferably a (111) surface, of a body of semiconductor material. The body of semiconductor material, preferably silicon, has two opposed major surfaces which are substantially parallel, the body is divided into four alternate regions of opposite type conductivity, the two end regions being emitter regions and the two middle regions being base regions when the body is employed as a light activated four region switch. Activating light enters at one major surface of the body, passes entirely through the body to the opposed major surface where light reflective etch pits cause the light to pass back through the body.
Inventors
- 👤 John S Roberts
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 16:26
CPC Classifications
H; H10; H10F; H10F30/00; H10F30/20; H10F30/21; H10F30/26; H10F30/263; G; G02; G02B; G02B6/00; G02B6/24; G02B6/26; G02B6/28; G02B6/2804; G02B6/2817; G02B6/42; G02B6/4201; G02B6/4202; G02B6/4295
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
158 words
A PROCESS FOR FORMING LIGHT RADIATION REFLECTING TETRAHEDRAL ETCH PITS IN A PRESELECTED SURFACE PORTION OF A BODY OF SILICON COMPRISING MASKING PRESELECTED SURFACE PORTIONS OF A BODY OF SILICON WITH A MATERIAL CAPABLE OF WITHSTANDING HYDROFLUORIC ACID, IMMERSING SAID BODY OF SILICON IN HYDROFLUORIC ACID TO REMOVE ANY OXIDES FROM THE UNMASKED SURFACE PORTION OF THE BODY, IMMERSING SAID BODY IN AN ETCHING SOLUTION FOR A PRESELECTED PERIOD OF TIME WHILE AGITATING THE SOLUTION RELATIVE TOSAID BODY, WHEREBY TETRAHEDRAL ETCH PITS AE FORMED IN THE UNMASKED SURFACE PORTION OF THE BODY SAID ETCHING SOLUTION HAVING BEEN PREPARED BY FORMING A FIRST SOLUTION BY ADMIXING 100 GRAMS OF CHROMIUM TRIOXIDE IN 100 MILLILITERS OF WATER AND JUST PRIOR TO ETCHING ADDING 100 MILLILITERS OF 49% HYDROFLUORIC ACID TO 100 MILLILITERS OF SAID FIRST SOLUTION, AND REMOV ING SAID BODY FROM SAID ETCHING SOLUTION QUENCHING SAID BODY WITH DEIONIZED WATER AND THEREAFTER REMOVING SAID MASKING MATERIAL FROM SAID BODY.
Claim 2
Dependent Claim
158 words
A PROCESS FOR FORMING LIGHT RADIATION REFLECTING TETRAHEDRAL ETCH PITS IN A PRESELECTED SURFACE PORTION OF A BODY OF SILICON COMPRISING MASKING PRESELECTED SURFACE PORTIONS OF A BODY OF SILICON WITH A MATERIAL CAPABLE OF WITHSTANDING HYDROFLUORIC ACID, IMMERSING SAID BODY OF SILICON IN HYDROFLUORIC ACID TO REMOVE ANY OXIDES FROM THE UNMASKED SURFACE PORTION OF THE BODY, IMMERSING SAID BODY IN AN ETCHING SOLUTION FOR A PRESELECTED PERIOD OF TIME WHILE AGITATING THE SOLUTION RELATIVE TOSAID BODY, WHEREBY TETRAHEDRAL ETCH PITS AE FORMED IN THE UNMASKED SURFACE PORTION OF THE BODY SAID ETCHING SOLUTION HAVING BEEN PREPARED BY FORMING A FIRST SOLUTION BY ADMIXING 100 GRAMS OF CHROMIUM TRIOXIDE IN 100 MILLILITERS OF WATER AND JUST PRIOR TO ETCHING ADDING 100 MILLILITERS OF 49% HYDROFLUORIC ACID TO 100 MILLILITERS OF SAID FIRST SOLUTION, AND REMOV ING SAID BODY FROM SAID ETCHING SOLUTION QUENCHING SAID BODY WITH DEIONIZED WATER AND THEREAFTER REMOVING SAID MASKING MATERIAL FROM SAID BODY.
Claim 3
Dependent Claim
16 words
The process of claim 1 in which the preselected time ranges from 5 to 10 minutes.
Claim 4
Dependent Claim
13 words
The process of claim 1 in which the preselected time is 7 minutes.
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) | 1978-11-17 | 1979-05-19 | 1979-11-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-17 | 1983-05-19 | 1983-11-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-17 | 1987-05-19 | 1987-11-18 | $7700.00 | Window Closed / Lapsed |