Patent US4537652A successfully refreshed from Google Patents.
US4537652A
Expired / Lapsed
US
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Process for preparing single crystal
Assignee: Sumitomo Electric Industries Ltd
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Filing: 1984-06-05
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Granted: 1985-08-27
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Expires: 2004-06-05
Abstract
Abstract A process for preparing a single crystal comprising drawing up a single crystal by the Czochralski process and cooling it at a temperature not lower than 600° C. at a reduced pressure or in vacuo, by which a single crystal having a dislocation density of 1.5×10 4 cm 2 or less is prepared.
Inventors
- 👤 Akihisa Kawasaki
- 👤 Kohji Tada
- 👤 Toshihiro Kotani
- 👤 Shintaro Miyazawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 23:00
CPC Classifications
C; C30; C30B; C30B15/00; C30B15/14
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
187 words
A process for preparing a single crystal comprising pulling up a single crystal by the Czochralski process and cooling it at a temperature not lower than 600° C. at a reduced pressure or in vacuo wherein the cooling step of the pulled single crystal comprises lowering the temperature at a rate of up to 5° C./min. to a temperature higher than 600° C., keeping the same temperature for 1 to 2 hours, reducing the pressure at the same temperature at a rate of up to 60 Kg/cm 2 /hr. to 1 to 3 kg/cm 2 , keeping the same pressure for 1 to 2 hours, lowering the temperature at the same pressure for 1 to 2 hours, lowering the temperature at the same pressure at a rate of up 5° C./min. to a temperature not lower than 600° C., reducing the pressure at the same temperature at a rate of up to 60 Kg/cm 2 /hr. to atmospheric pressure, evacuating at a rate of up to 10 Torr/min. to a pressure of 10 -2 Torr. or lower, and keeping the same vacuum for 1 to 2 hours.
Claim 2
Dependent Claim
187 words
A process for preparing a single crystal comprising pulling up a single crystal by the Czochralski process and cooling it at a temperature not lower than 600° C. at a reduced pressure or in vacuo wherein the cooling step of the pulled single crystal comprises lowering the temperature at a rate of up to 5° C./min. to a temperature higher than 600° C., keeping the same temperature for 1 to 2 hours, reducing the pressure at the same temperature at a rate of up to 60 Kg/cm 2 /hr. to 1 to 3 kg/cm 2 , keeping the same pressure for 1 to 2 hours, lowering the temperature at the same pressure for 1 to 2 hours, lowering the temperature at the same pressure at a rate of up 5° C./min. to a temperature not lower than 600° C., reducing the pressure at the same temperature at a rate of up to 60 Kg/cm 2 /hr. to atmospheric pressure, evacuating at a rate of up to 10 Torr/min. to a pressure of 10 -2 Torr. or lower, and keeping the same vacuum for 1 to 2 hours.
Claim 3
Dependent Claim
28 words
A process according to claim 1, wherein the single crystal is that of a semiconducting compound selected from the group consisting of GaP, GaAs, InP, ZnSe and CdS.
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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) | 1988-08-26 | 1989-02-25 | 1989-08-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-08-26 | 1993-02-25 | 1993-08-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-08-26 | 1997-02-25 | 1997-08-27 | $7700.00 | Window Closed / Lapsed |