US4548654A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Surface denuding of silicon wafer
Assignee: NXP USA Inc
•
Filing: 1983-06-03
•
Granted: 1985-10-22
•
Expires: 2003-06-03
Abstract
Abstract A process is disclosed for preparing silicon wafers having a high quality, high lifetime surface layer and a bulk region characterized by a low lifetime and by a high density of precipitated oxygen gettering sites. A wafer having a relatively high concentration of interstitial oxygen is heated in a reducing ambient at a sufficiently high temperature and a sufficiently long time to cause a surface layer to be denuded of oxygen related defects and dislocations. The temperature is then ramped down to a lower temperature and the wafer is maintained at this lower temperature for a sufficient time to allow precipitation of oxygen within the bulk of the wafer.
Inventors
- 👤 Philip J. Tobin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 07:37
CPC Classifications
H; H10; H10P; H10P95/00; H10P36/00; H10P36/20; Y; Y10; Y10S; Y10S148/00; Y10S148/023; Y10S148/024
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
82 words
A process for preparing a silicon substrate for the fabrication of a device which comprises the steps of: providing a silicon substrate having a concentration of oxygen incorporated therein; heating said substrate to a first elevated temperature in a reducing ambient; lowering the temperature of said substrate to a second elevated temperature lower than said first elevated temperature; and maintaining said substrate at said second elevated temperature for a time to allow nucleation of oxygen precipitates in the bulk of said substrate.
Claim 2
Dependent Claim
82 words
A process for preparing a silicon substrate for the fabrication of a device which comprises the steps of: providing a silicon substrate having a concentration of oxygen incorporated therein; heating said substrate to a first elevated temperature in a reducing ambient; lowering the temperature of said substrate to a second elevated temperature lower than said first elevated temperature; and maintaining said substrate at said second elevated temperature for a time to allow nucleation of oxygen precipitates in the bulk of said substrate.
Claim 3
Dependent Claim
11 words
The process of claim 1 wherein said reducing ambient comprises hydrogen.
Claim 4
Dependent Claim
16 words
The process of claim 2 wherein said reducing ambient comprises hydrogen diluted with argon or helium.
Claim 5
Dependent Claim
16 words
The process of claim 1 wherein said concentration of oxygen exceed 1.3×10 18 cm -3 .
Claim 6
Dependent Claim
20 words
The process of claim 1 wherein said first temperature comprises a temperature between about 1000° C. and about 1200° C.
Claim 7
Dependent Claim
14 words
The process of claim 1 wherein said second elevated temperature is about 600°-800° C.
Claim 8
Dependent Claim
13 words
The process of claim 5 wherein said first temperature is about 1100°-1150° C.
Claim 9
Dependent Claim
34 words
The process of claim 6 further comprising the step of heating said substrate to a temperature intermediate said first and second temperatures in an oxidizing ambient to grow an oxide layer on said substrate.
Claim 10
Dependent Claim
128 words
A process for fabricating a semiconductor device which comprises the steps of: providing a silicon wafer of first conductivity type having a concentration of oxygen incorporated therein; heating said wafer to a temperature between about 1000° and 1200° C. in a reducing ambient for a sufficient time to form a denuded surface layer on said wafer; heating said wafer in an oxidizing ambient to form a protective oxide on the surface thereof; reducing the temperature of said wafer to a second temperature between about 600° and 800° C. to nucleate the precipitation of oxygen in the bulk of said wafer; and forming regions of second conductivity type in said denuded surface layer, said regions having a depth into said wafer less than the thickness of said surface layer.
Claim 11
Dependent Claim
128 words
A process for fabricating a semiconductor device which comprises the steps of: providing a silicon wafer of first conductivity type having a concentration of oxygen incorporated therein; heating said wafer to a temperature between about 1000° and 1200° C. in a reducing ambient for a sufficient time to form a denuded surface layer on said wafer; heating said wafer in an oxidizing ambient to form a protective oxide on the surface thereof; reducing the temperature of said wafer to a second temperature between about 600° and 800° C. to nucleate the precipitation of oxygen in the bulk of said wafer; and forming regions of second conductivity type in said denuded surface layer, said regions having a depth into said wafer less than the thickness of said surface layer.
Claim 12
Dependent Claim
122 words
A process for preparing a silicon substrate for the fabrication of a device which comprises the steps of: providing a silicon wafer having a concentration of oxygen greater than about 1.3×10 18 cm -3 incorporated therein; heating said wafer to a first elevated temperature; annealing said wafer in a reducing ambient at said first elevated temperature for about 1-4 hours; cooling said wafer to a second temperature lower than said first elevated temperature; maintaining said wafer at said second temperature in an oxidizing ambient to form an oxide layer on said wafer; further cooling said wafer to a third temperature lower than said second temperature; and maintaining said wafer at said third temperature for a sufficient time for the nucleation of microprecipitates.
Claim 13
Dependent Claim
122 words
A process for preparing a silicon substrate for the fabrication of a device which comprises the steps of: providing a silicon wafer having a concentration of oxygen greater than about 1.3×10 18 cm -3 incorporated therein; heating said wafer to a first elevated temperature; annealing said wafer in a reducing ambient at said first elevated temperature for about 1-4 hours; cooling said wafer to a second temperature lower than said first elevated temperature; maintaining said wafer at said second temperature in an oxidizing ambient to form an oxide layer on said wafer; further cooling said wafer to a third temperature lower than said second temperature; and maintaining said wafer at said third temperature for a sufficient time for the nucleation of microprecipitates.
Claim 14
Dependent Claim
19 words
The process of claim 10 wherein said first elevated temperature is between about 1000° C. and about 1200° C.
Claim 15
Dependent Claim
18 words
The process of claim 11 wherein said third temperature is between about 600° C. and about 800° C.
Claim 16
Dependent Claim
13 words
The process of claim 12 wherein said third temperature is about 750° C.
Claim 17
Dependent Claim
14 words
The process of claim 12 wherein said first elevated temperature is about 1100° C.
References Cited (Backward Citations)
US4116719A
Cited
US4220483A
Cited
US4314595A
Cited
US4376657A
Cited
GB2080780A
Cited
US4364779A
Cited
EP0060676A2
Cited
EP0066461A2
Cited
US4437922A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-10-21 | 1989-04-22 | 1989-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-21 | 1993-04-22 | 1993-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-21 | 1997-04-22 | 1997-10-22 | $7700.00 | Window Closed / Lapsed |