US3615261A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of producing single semiconductor crystals
Assignee: Motorola Solutions Inc
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Filing: 1969-04-02
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Granted: 1971-10-26
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Expires: 1989-04-02
Abstract
Abstract A method of making an ingot length of a single semiconductive crystal having substantially uniform resistivity throughout most of the length of the ingot is disclosed. An inert helium atmosphere is placed about a mass of silicon material and then the silicon mass is melted. A seed of silicon is inserted into the melt and withdrawn at a rate which provides a substantially uniform ingot diameter. As the seed is withdrawn from the melt, the pressure in the system is slowly reduced to vaporize the impurity from the melt so as to maintain a substantially constant impurity concentration in the melt during the formation of the ingot.
Inventors
- 👤 Donald R Causey
- 👤 John R Lenzing
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 21:45
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/02; C30B29/06; C30B15/00; C30B15/20; Y; Y10; Y10S; Y10S148/00; Y10S148/041; Y10S148/107; Y10S438/00; Y10S438/909; Y10S438/914; Y10S438/925
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
22 words
A method as described in claim 1 wherein said inert gas atmosphere is taken from the group consisting of helium and argon.
Claim 2
Dependent Claim
21 words
A method as described in claim 1 wherein said impurity is taken from the group consisting of phosphorus, arsenic, and antimony.
Claim 3
Independent Claim
166 words
A method of making a single semiconductive crystal having a predetermined resistivity comprising the steps of: a. providing a mass of semiconductive material selected from the group consisting of germanium and silicon and containing conductivity-type impurity having a vapor pressure above that of said material, b. passing a gas taken from the group consisting of helium and argon about said mass at a flow rate of about 20 to 30 cubic feet per hour, c. melting said mass, d. inserting a seed of said mass material into said melted mass, e. withdrawing said seed at a rate such that the semiconductive material from the melt forms a single crystal propagated from said seed crystal, f. reducing the flow rate of said gas during said withdrawing step, and g. (reducing the pressure) during said withdrawing step, reducing the pressure of said inert gas atmosphere at a rate and to a value determined by said predetermined resistivity to maintain a substantially constant impurity concentration in said melted mass.
Claim 4
Dependent Claim
26 words
A method as described in claim 4 wherein said gas flow is reduced to less than 1 cubic foot per hour in 30 to 90 minutes.
Claim 5
Dependent Claim
26 words
A method as described in claim 4 wherein the pressure is reduced from between 50 to 760 mm. Hg to 1 X 10 4 mm. Hg.
Claim 6
Dependent Claim
69 words
The method according to claim 1 wherein at the initiation of the withdrawing step, the inert gas atmosphere has a predetermined value and b. the rate of reduction of pressure of said inert atmosphere comprises a rate reduction from said predetermined pressure value to a lower value determined by said predetermined resistivity and a continuation of the said lower value of pressure during the remaining withdrawal of said crystal.
Claim 7
Dependent Claim
69 words
The method according to claim 4 wherein a. at the initiation of the withdrawing step, the inert gas atmosphere has a predetermined pressure value and b. the rate of reduction of pressure of said inert atmosphere comprises a rate reduction from said predetermined pressure value to a lower value determined by said predetermined resistivity and a continuation of said lower pressure value during the remaining withdrawal of said crystal.
Claim 8
Dependent Claim
68 words
The method according to claim 6 wherein the reduction in pressure is in two stages comprising a. a reduction from between 50 to 760 mm. Hg to between 1to 1 X 10 4 mm. Hg during a portion of the crystal pulling process and b. a continuation of the pressure between 10 to 1 X 10 4 mm. Hg throughout the remaining portion of the crystal withdrawal process.
Claim 9
Dependent Claim
62 words
The method according to claim 6 wherein the reduction of pressure from between 50 to 760 mm. Hg to about 1 mm. Hg is at a linear rate with respect to time and the reduction from about 1 mm. Hg to 1 X 10 4 mm. Hg is exponential as determined by the needle valve construction being closed at a normal rate.
References Cited (Backward Citations)
US3501406A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-10-25 | 1975-04-26 | 1975-10-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-10-25 | 1979-04-26 | 1979-10-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-10-25 | 1983-04-26 | 1983-10-26 | $7700.00 | Window Closed / Lapsed |