US4525336A
Expired / Lapsed
US
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Process for removing impurities from silicon fragments
Assignee: Siltronic AG
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Filing: 1984-05-29
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Granted: 1985-06-25
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Expires: 2004-05-29
Abstract
Abstract A process for the removal of carbon- and iron-containing impurities from icon fragments which result when polycrystalline formed silicon bodies produced by vapor phase deposition undergo a crushing treatment. The removal is effected by several steps comprising nitrate treatment, annealing, acid and magnetic treatment, leaving the treated fragments in a state of highest purity that makes them particularly useful in the crucible-pulling process of Czochralski.
Inventors
- 👤 Rudolf Griesshammer
- 👤 Michael Peterat
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 23:53
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/02; C30B29/06; C01; C01B; C01B33/00; C01B33/02; C01B33/021; C01B33/027; C01B33/035; C01B33/037; C30B15/00
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
53 words
A process for removing impurities from silicon fragments which result when polycrystalline silicon formed bodies are subjected to a crushing treatment, said process comprising the steps of: (a) treating the silicon fragments with an aqueous solution of nitrate salts; (b) annealing the so-treated fragments; and, (c) treating the annealed fragments with hydrofluoric acid.
Claim 2
Dependent Claim
53 words
A process for removing impurities from silicon fragments which result when polycrystalline silicon formed bodies are subjected to a crushing treatment, said process comprising the steps of: (a) treating the silicon fragments with an aqueous solution of nitrate salts; (b) annealing the so-treated fragments; and, (c) treating the annealed fragments with hydrofluoric acid.
Claim 3
Dependent Claim
18 words
The process of claim 1, additionally including the step of (d) removing iron-containing impurities from said silicon fragments.
Claim 4
Dependent Claim
26 words
The process of claim 1, wherein said aqueous nitrate solution is a member selected from the group consisting of sodium nitrate solution and potassium nitrate solution.
Claim 5
Dependent Claim
18 words
The process of claim 1, wherein step (b) is carried out at temperatures between 1000° and 1100° C.
Claim 6
Dependent Claim
33 words
The process of claim 2, wherein step (d) is effected by treatment in said fragments with a member of the group consisting of hydrochloric acid, nitric acid and a mixture of these acids.
Claim 7
Dependent Claim
11 words
The process of claim 2, wherein step (d) precedes steps (a)-(c).
Claim 8
Dependent Claim
16 words
The process of claim 2, wherein step (d) is effected by magnetically separating said iron-containing impurities.
Claim 9
Dependent Claim
25 words
The process of claim 7, wherein step (d) is effected by both magnetically separating said iron-containing impurities and by heating said fragments with an acid.
Claim 10
Dependent Claim
33 words
The process of claim 1, wherein said aqueous solution of nitrate salts, in step (a), is selected from the group consisting of lithium nitrate, calcium nitrate, strontium nitrate, barium nitrate, and mixtures thereof.
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) | 1988-06-24 | 1988-12-24 | 1989-06-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-06-24 | 1992-12-24 | 1993-06-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-06-24 | 1996-12-24 | 1997-06-25 | $7700.00 | Window Closed / Lapsed |