Patent US4437922A successfully refreshed from Google Patents.
US4437922A
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US
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Method for tailoring oxygen precipitate particle density and distribution silicon wafers
Assignee: International Business Machines Corp
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Filing: 1982-03-26
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Granted: 1984-03-20
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Expires: 2002-03-26
Abstract
Abstract A wide precipitate-free-zone (PFZ) is formed at the surface of a semiconductor substrate and at the same time a high density of oxygen precipitate particles are produced beneath at the surface PFZ by a two step annealing process involving a first cycle of very rapidly heating the wafers to a first high temperature and a second cycle of very slowly heating the wafers to a second high temperature.
Inventors
- 👤 Bernard K. Bischoff
- 👤 William J. Patrick
- 👤 Thomas H. Strudwick
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:25
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/02; C30B29/06; C30B33/00; H; H10; H10P; H10P36/00; H10P36/20; Y; Y10; Y10S; Y10S148/00; Y10S148/024
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
134 words
A method for tailoring oxygen precipitate particle density and distribution in a silicon wafer, comprising the steps of: heating the silicon wafer to a first high temperature at a rate higher than 10° C./minute, said first high temperature being sufficiently high to reduce the number of pre-existing oxygen clusters, keeping said wafer at said first high temperature for a period sufficient to allow outdiffusion of oxygen, allowing said wafer to cool, annealing said wafer at a low temperature, said low temperature being sufficiently low to nuceleate precipitated oxygen, and heating said wafer to a second high temperature at a rate lower than 2° C./minute, said second high temperature being sufficiently high to grow the precipitated oxygen nucleated at said low temperature to a size which ensures survival of the precipitated oxygen in subsequent processing.
Claim 2
Independent Claim
134 words
A method for tailoring oxygen precipitate particle density and distribution in a silicon wafer, comprising the steps of: heating the silicon wafer to a first high temperature at a rate higher than 10° C./minute, said first high temperature being sufficiently high to reduce the number of pre-existing oxygen clusters, keeping said wafer at said first high temperature for a period sufficient to allow outdiffusion of oxygen, allowing said wafer to cool, annealing said wafer at a low temperature, said low temperature being sufficiently low to nuceleate precipitated oxygen, and heating said wafer to a second high temperature at a rate lower than 2° C./minute, said second high temperature being sufficiently high to grow the precipitated oxygen nucleated at said low temperature to a size which ensures survival of the precipitated oxygen in subsequent processing.
Claim 3
Dependent Claim
16 words
The method of claim 1 wherein said low temperature is between 400° C. and 500° C.
Claim 4
Dependent Claim
17 words
The method of claim 2 wherein said second high temperature is between 750° C. and 1000° C.
Claim 5
Dependent Claim
17 words
The method of claim 3 wherein said first high temperature is between 1000° C. and 1400° C.
Claim 6
Dependent Claim
32 words
The method of claim 4 wherein said wafer is heated up to said first high temperature by inserting said wafer into a furnace which is already substantially at said first high temperature.
Claim 7
Dependent Claim
19 words
The method of claim 5 wherein said wafer is kept at said first high temperature for approximately four hours.
Claim 8
Dependent Claim
32 words
The method of claim 5 wherein the wafer cooling step comprises the steps of: ramping down from said first high temperature to approximately 800° C. and removing said wafer from the furnace.
Claim 9
Independent Claim
126 words
A method for tailoring oxygen precipitate particle density and distribution in a silicon wafer, comprising the steps of: heating the silicon wafer to a first high temperature at a rate higher than 10° C./minute, said first high temperature being sufficiently high to reduce the number of pre-existing oxygen clusters, keeping said wafer at said first high temperature for a period sufficient to allow outdiffusion of oxygen, allowing said wafer to cool, annealing said wafer at a low temperature, said low temperature being sufficiently low to nucleate precipitated oxygen, heating said wafer to a temperature in the range of 750° C. to 850° C. at a rate lower than 2° C./minute, and heating said wafer to a temperature in the range of 900° C. to 1000° C.
Claim 10
Independent Claim
126 words
A method for tailoring oxygen precipitate particle density and distribution in a silicon wafer, comprising the steps of: heating the silicon wafer to a first high temperature at a rate higher than 10° C./minute, said first high temperature being sufficiently high to reduce the number of pre-existing oxygen clusters, keeping said wafer at said first high temperature for a period sufficient to allow outdiffusion of oxygen, allowing said wafer to cool, annealing said wafer at a low temperature, said low temperature being sufficiently low to nucleate precipitated oxygen, heating said wafer to a temperature in the range of 750° C. to 850° C. at a rate lower than 2° C./minute, and heating said wafer to a temperature in the range of 900° C. to 1000° C.
Claim 11
Independent Claim
145 words
A method for tailoring oxygen precipitate particle density and distribution in a silicon wafer, comprising the steps of: heating the silicon wafer to a first high temperature at a rate higher than 10° C./minute, said first high temperature being sufficiently high to reduce the number of pre-existing oxygen clusters, keeping said wafer at said first high temperature for a period sufficient to allow outdiffusion of oxygen, allowing said wafer to cool, annealing said wafer at a low temperature, said low temperature being sufficiently low to nucleate precipitated oxygen, heating said wafer to a second high temperature of approximately 650° C. at a rate lower than 2° C./minute, keeping said wafer at said second high temperature for a time sufficient to grow precipitate particles, and heating said wafers to a third high temperature in the range of 750° C. to 850° C. at a higher rate.
Claim 12
Independent Claim
145 words
A method for tailoring oxygen precipitate particle density and distribution in a silicon wafer, comprising the steps of: heating the silicon wafer to a first high temperature at a rate higher than 10° C./minute, said first high temperature being sufficiently high to reduce the number of pre-existing oxygen clusters, keeping said wafer at said first high temperature for a period sufficient to allow outdiffusion of oxygen, allowing said wafer to cool, annealing said wafer at a low temperature, said low temperature being sufficiently low to nucleate precipitated oxygen, heating said wafer to a second high temperature of approximately 650° C. at a rate lower than 2° C./minute, keeping said wafer at said second high temperature for a time sufficient to grow precipitate particles, and heating said wafers to a third high temperature in the range of 750° C. to 850° C. at a higher rate.
Claim 13
Dependent Claim
17 words
The method of claim 9 wherein the time sufficient to grow precipitate particles is about sixteen hours.
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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) | 1987-03-20 | 1987-09-19 | 1988-03-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-20 | 1991-09-19 | 1992-03-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-20 | 1995-09-19 | 1996-03-20 | $7700.00 | Window Closed / Lapsed |