US4537652A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Process for preparing single crystal
Assignee: Sumitomo Electric Industries Ltd
•
Filing: 1984-06-05
•
Granted: 1985-08-27
•
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 10:24
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.
References Cited (Backward Citations)
US3623905A
Cited
US3647389A
Cited
US4190486A
Cited
US4140570A
Cited
DD132704A3
Cited
US4141779A
Cited
DD134423A3
Cited
US4234355A
Cited
WO1981001016A1
Cited
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 |