US3795488A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for producing crystal boules with extensive flat, parallel facets
Assignee: General Electric Co
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Filing: 1971-02-01
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Granted: 1974-03-05
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Expires: 1991-02-01
Abstract
Abstract A particular symmetric anisotropic temperature distribution is established at the crystal-melt interface and the seed crystal is pulled from the melt to produce a crystal boule. The seed crystal is oriented in a specific crystallographic direction and is prevented from rotation with respect to the temperature symmetry axes while being withdrawn from the melt. The temperature distribution is such that the temperature varies slowly with varying distance from the center of the crystal boule along a first axis defining the crystal boule width, and varies rapidly with distance along a second axis perpendicular to the first and which defines the crystal boule thickness. The maintenance of the particular anisotropic temperature distribution at the crystalmelt interface produces a single crystal boule with a pair of extensive flat, parallel facets that are microscopically smooth.
Inventors
- 👤 D Oliver
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 22:40
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/10; C30B29/16; C30B29/22; C30B15/00; C30B15/14; Y; Y10; Y10S; Y10S117/00; Y10S117/901; Y10S117/902
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
117 words
The method set forth in claim 1 wherein the step of increasing the temperature with increasing distance from the center of the crystal boule along the second axis consists of increasing the temperature at substantially the same slow rate as the temperature along the first axis for a distance up to t/2 where t is the crystal boule thickness, and increasing at a substantially faster rate for distances beyond t/2 from the center of the crystal boule, the particular symmetric anisotropic temperature distribution and crystal boule orientation causing the crystal boule to preferably vary in dimension along the first axis rather than along the second axis in response to inherent small temperature fluctuations at the crystal-melt interface.
Claim 2
Dependent Claim
69 words
The method set forth in claim 1 and further comprising the step of cutting the grown crystal boule to predetermined dimensions to thereby utilize the crystal formed by the cutting process in a device requiring two surfaces that are flat, microscopically smooth, free from mechanical damage and accurately parallel, the microscopically smooth surfaces requiring no further polishing or cleaving process whereby the crystal is utilized directly in the device.
Claim 3
Dependent Claim
110 words
The method set forth in claim 1 wherein the step of establishing a particular symmetric anisotropic temperature distribution consists of establishing first temperature zones slightly higher than the average melt temperature along the crystalmelt interface associated with nonfaceting surfaces of the crystal boule whereby the temperature increases slowly with increasing distance from the center of the crystal boule along the first axis thereof, and establishing equal second temperature zones higher than the first temperature along the crystal-melt interface associated with the pair of strongly faceting surfaces of the crystal boule whereby the temperature increases rapidly with increasing distance from the center of the crystal boule along the second axis thereof.
Claim 4
Dependent Claim
113 words
The method set forth in claim 4 wherein the step of orienting the seed crystal consists of aligning the first axis of the seed crystal with the normal to the nonfaceting surfaces of the seed crystal, and aligning the second axis of the seed crystal with the normal to the faceting surfaces of the seed crystal, the symmetric anisotropic temperature distribution and crystal orientation causing the growing crystal boule to vary in dimension preferably along the nonfaceting surfaces thereof and thereby substantially avoid formation of growth steps on the faceting surfaces in response to inherent small temperature fluctuation at the crystal-melt interface whereby the faceting surfaces are microscopically smooth along extensive regions thereof.
Claim 5
Dependent Claim
72 words
The method set forth in claim 4 wherein the step of establishing the particular symmetric anisotropic temperature distribution consists of disposing an auxiliary heating device spaced slightly above the top surface of the melt and arranged with the heating element thereof parallel to, and spaced slightly from, the facet surfaces of the seed crystal and resultant crystal boule which is withdrawn from the melt between portions of the auxiliary device heating element.
References Cited (Backward Citations)
US2809136A
Cited
US2927008A
Cited
US3031275A
Cited
US3124489A
Cited
US3453352A
Cited
US3293002A
Cited
US3617223A
Cited
US3607115A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-03-04 | 1977-09-03 | 1978-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-04 | 1981-09-03 | 1982-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-04 | 1985-09-03 | 1986-03-05 | $7700.00 | Window Closed / Lapsed |