Patent US3923567A successfully refreshed from Google Patents.
US3923567A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of reclaiming a semiconductor wafer
Assignee: Silicon Materials Inc
•
Filing: 1974-08-09
•
Granted: 1975-12-02
•
Expires: 1994-08-09
Abstract
Abstract A method of reclaiming a semiconductor wafer wherein wafers which have been rejected due to electrical failures or visual defects can be processed to form a purer wafer capable of providing above average yields. The method comprises the steps of gettering to draw undesired point defects (impurities and vacancies) toward the wafer surface and chemical etching to remove most of the point defects whose presence in silicon would lower semiconductor yields. Other steps include grinding the back surface of the wafer to form an insitu getter region and finally polishing the front of the wafer to form a strain-free mirrorlike finish.
Inventors
- 👤 John E Lawrence
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 23:52
CPC Classifications
H; H10; H10P; H10P90/00; H10P90/12; H10P90/16; H10P36/00; H10P36/03; H10P95/00; Y; Y10; Y10S; Y10S148/00; Y10S148/061
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
55 words
A METHOD OF RECLAIMING A SEMICONDUCTOR WAFER COMPRISING THE STEPS OF: STRIPPING ALL EXTERNAL LAYERS FROM SAID WAFER, GETTERING SAID WAFTER SO AS TO DRAW EXCESS POINT DEFECTS TOWARDS THE SURFACES OF SAID WAFER, AND ETCHING THE SURFACES OF SAID WAFER SO AS TO EFFECTIVELY REMOVE THE CONTAMINANTS THAT WERE DRAWN TOWARD SAID WAFTER SURFACES.
Claim 2
Dependent Claim
39 words
A method of reclaiming a semiconductor wafer as recited in claim 1 including following termination of the etching step the step of grinding one face of the wafer so as to generate a massive source of surface lattice strain.
Claim 3
Dependent Claim
23 words
A method of reclaiming a semiconductor wafer as recited in claim 2 including the step of polishing the other face of said wafer.
Claim 4
Dependent Claim
58 words
A method of reclaiming a semiconductor wafer as recited in claim 1 wherein the step of stripping includes the steps of placing said wafer in a boat and immersing said boat in baths consisting of sulphuric acid to remove organic material, hydrochloric acid and nitric acid to remove metallic materials, and hydrofluoric acid to remove oxides and nitrides.
Claim 5
Dependent Claim
72 words
A method of reclaiming a semiconductor wafer as recited in claim 1 wherein the step of gettering includes the substeps of heating said wafer to a temperature below the melting temperature of said semiconductor material such that excess point defects within said wafer are caused to move toward said surfaces and forming a layer of phosphorus over said surfaces thereby generating a strain and causing said impurities to form near said surfaces.
Claim 6
Dependent Claim
32 words
A method of reclaiming a semiconductor wafer as recited in claim 5 wherein during said heating sub-step said wafer is heated to a temperature in the range of between 850*C and 1150*C.
Claim 7
Dependent Claim
51 words
A method of reclaiming a semiconductor wafer as recited in claim 5 wherein the step of forming a layer of phosphorus includes directing a stream of a gaseous phosphorus compound over said surfaces until a high concentration of phosphorus is diffused to a depth of about 2 microns into saId wafer.
Claim 8
Dependent Claim
27 words
A method of reclaiming a semiconductor wafer as recited in claim 1 wherein the step of etching removes at least 0.1 mil from each of said surfaces.
Claim 9
Dependent Claim
40 words
A method of reclaiming a semiconductor wafer as recited in claim 1 wherein the step of etching includes placing said wafer in a liquid comprising a concentrated acid which has a characteristic etching rate of about 12 microns/minute/side at 25*C.
Claim 10
Dependent Claim
45 words
A method of reclaiming a semiconductor wafer as recited in claim 1 wherein the step of etching includes placing said wafer in a liquid comprising 1 part of hydrofluoric acid, 3 parts of nitric acid, 4 parts of a mixture of acetic acid, and iodine.
Claim 11
Dependent Claim
43 words
A method of reclaiming a semiconductor wafer as recited in claim 1 including the steps of measuring the thickness of said etched wafers, separating said measured wafers into groups having a 0.1 mil thickness variation, and polishing the other face of said wafer.
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) | 1978-12-01 | 1979-06-02 | 1979-12-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-01 | 1983-06-02 | 1983-12-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-01 | 1987-06-02 | 1987-12-02 | $7700.00 | Window Closed / Lapsed |