US4040895A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Control of oxygen in silicon crystals
Assignee: International Business Machines Corp
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Filing: 1975-10-22
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Granted: 1977-08-09
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Expires: 1995-10-22
Abstract
Abstract The seed to tail oxygen concentration gradient in silicon crystals, which are drawn from a silicon melt contained in a silica vessel according to the Czochralski process, is controlled by a process employing stop-go crucible rotation to provide fluid shearing at the melt-crucible interface.
Inventors
- 👤 William John Patrick
- 👤 Wolfgang Alfred Westdorp
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 15:31
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/02; C30B29/06; C30B15/00; Y; Y10; Y10S; Y10S117/00; Y10S117/916
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
157 words
A process for controlling the oxygen content gradient in a silicon crystal, which is drawn from a melt of silicon contained in a silica crucible, comprising: continuously rotating the crystal as it is drawn from the melt, while rotating the crucible in a direction opposite to the direction of crystal rotation with the rate of crucible rotation ranging from about 5 to 20 rpm; and controlling the oxygen concentration of the melt during the crystal growing process by periodically stopping the rotation of the crucible, to create fluid shearing at the melt-crucible interface, in regular on time/off time duty cycles in which the on time and the off time each range from about 1 to 15 seconds with the duty cycles and the rate of crucible rotation being selected such that adverse effects on crystal quality do not occur while the oxygen concentration gradient in the silicon crystal is kept to about 4×10 17 atoms/cc or less.
Claim 2
Dependent Claim
157 words
A process for controlling the oxygen content gradient in a silicon crystal, which is drawn from a melt of silicon contained in a silica crucible, comprising: continuously rotating the crystal as it is drawn from the melt, while rotating the crucible in a direction opposite to the direction of crystal rotation with the rate of crucible rotation ranging from about 5 to 20 rpm; and controlling the oxygen concentration of the melt during the crystal growing process by periodically stopping the rotation of the crucible, to create fluid shearing at the melt-crucible interface, in regular on time/off time duty cycles in which the on time and the off time each range from about 1 to 15 seconds with the duty cycles and the rate of crucible rotation being selected such that adverse effects on crystal quality do not occur while the oxygen concentration gradient in the silicon crystal is kept to about 4×10 17 atoms/cc or less.
Claim 3
Dependent Claim
21 words
The process of claim 1 wherein the on time/off time duty cycles range from 15 seconds/1 second to 2 seconds/1 second.
Claim 4
Dependent Claim
18 words
The process of claim 1 wherein the on time/off duty cycle is 5 seconds/5 seconds within ± 50%
Claim 5
Dependent Claim
11 words
A silicon crystal grown according to the process of claim 1.
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) | 1980-08-08 | 1981-02-07 | 1981-08-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-08-08 | 1985-02-07 | 1985-08-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-08-08 | 1989-02-07 | 1989-08-09 | $7700.00 | Window Closed / Lapsed |