CA2000243A1
Expired / Lapsed
CA
⏱️ 0.0 years remaining
Method of growing silicon ingots using a rotating melt
Assignee: Crystal Systems Inc USA
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Filing: 1989-10-06
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Granted: —
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Expires: 2009-10-06
Abstract
Abstract Abstract of the Disclosure The invention is a method and apparatus for producing silicon ingots of substantially single crystallinity from metallurgical grade silicon by heating it in a crucible to above its melting point to melt it and then extracting heat from the bottom of the crucible with a heat exchanger in heat conducting relationship with the bottom, and by moving the crucible and growing crystal in a first direction and accelerating the motion, thereby detaching from the crystal/liquid interface adhered impurity particles. The crucible may be rotated and the acceleration may be rotational.
Inventors
- 👤 Frederick Schmid
- 👤 Chandra P. Khattak
Bibliographic Details
Application Number
—
Jurisdiction
CA
Data Source
google_patents
Last Synchronized
2026-11-09 03:25
CPC Classifications
C; C30; C30B; C30B29/00; C30B29/02; C30B29/06; C30B11/00; C30B11/008
Claims Analysis
Total Claims: 23
Claim 1
Independent Claim
151 words
A process for producing a silicon ingot of substantially single crystallinity suitable for use in photovoltaic cells from low purity silicon meltstock, said process comprising the steps of: a. providing a silicon meltstock having an impurity level greater than 10,000 ppm by weight; b. heating said silicon meltstock in a crucible to above its melting point; c. thereafter solidifying said melted silicon meltstock to product said ingot by extracting heat from a central portion of the bottom of said crucible whereby impurity particles are excluded from the solidified meltstock forming the interior of said ingot subsequent to said heating and in the course of said solidifying and adhere loosely to the surface of the growing solid; and d. periodically, ii. rotating said solidifying melt in a first direction; and iii. thereafter decelerating the rotation of the meltstock sufficiently abruptly to dislodge said adhered impurities from the solidified portion of the meltstock.
Claim 2
Dependent Claim
151 words
A process for producing a silicon ingot of substantially single crystallinity suitable for use in photovoltaic cells from low purity silicon meltstock, said process comprising the steps of: a. providing a silicon meltstock having an impurity level greater than 10,000 ppm by weight; b. heating said silicon meltstock in a crucible to above its melting point; c. thereafter solidifying said melted silicon meltstock to product said ingot by extracting heat from a central portion of the bottom of said crucible whereby impurity particles are excluded from the solidified meltstock forming the interior of said ingot subsequent to said heating and in the course of said solidifying and adhere loosely to the surface of the growing solid; and d. periodically, ii. rotating said solidifying melt in a first direction; and iii. thereafter decelerating the rotation of the meltstock sufficiently abruptly to dislodge said adhered impurities from the solidified portion of the meltstock.
Claim 3
Dependent Claim
13 words
The process of claim 1 wherein said adhered impurities are of silicon carbide.
Claim 4
Dependent Claim
20 words
The process of claim 2 where said silicon meltstock is metallurgical grade silicon produced by the carbothermic reduction of silica.
Claim 5
Dependent Claim
57 words
The process of claim 1 including the step of providing silica within said crucible prior to said solidifying, and wherein said impurities are removed from said meltstock by the step of reacting said silica with silicon carbide impurities in said silicon meltstock to cause the formation of reaction products that will separate from the melted silicon meltstock.
Claim 6
Dependent Claim
20 words
The process of claim 4 wherein before heating said silicon meltstock, said meltstock includes an adherent covering layer of silica.
Claim 7
Dependent Claim
24 words
The process of claim 4 wherein said silica is added to said melted silicon meltstock subsequent to said heating and prior to said solidifying.
Claim 8
Dependent Claim
12 words
The process of claim 6 wherein said silica is pure powdered silica.
Claim 9
Dependent Claim
42 words
The process of claim 1 including the step of reacting non-volatile impurities in said melt stock to form volatile impurities, and removing said volatile impurities from said silicon meltstock by reducing the pressure around said crucible to less than about 30 torr.
Claim 10
Dependent Claim
13 words
The process of claim 8 wherein said reduced pressure is about 0.1 torr.
Claim 11
Dependent Claim
31 words
The process of claim 8 including the step of heating said silicon to between about 50°C to 100°C. above the melting point of silicon to promote said removal of volatile impurities.
Claim 12
Dependent Claim
28 words
The process of claim 8 wherein said volatile impurities are produced by passing moist gas chosen from the group of hydrogen and chlorine through said melted silicon melt.
Claim 13
Dependent Claim
21 words
The process of claim 8 wherein said volatile impurities are produced by adding silica to said meltstock. What is claimed is:
Claim 14
Dependent Claim
149 words
A process for producing a silicon ingot of large grain size multiple crystallinity suitable for use in photovoltaic cells from low purity silicon meltstock, said process comprising the steps of: a. providing a silicon meltstock having an impurity level greater than 10,000 ppm by weight; b. heating said silicon meltstock in a crucible to above its melting point; c. thereafter solidifying said melted silicon meltstock to product said ingot by extracting heat from the bottom of said crucible whereby impurity particles are excluded from the solidified meltstock forming the interior of said ingot subsequent to said heating and in the course of said solidifying and adhere loosely to the surface of the growing solid; and d. periodically, ii. rotating said solidifying melt in a first direction; and iii. thereafter decelerating the rotation of the meltstock sufficiently abruptly to dislodge said adhered impurities from the solidified portion of the meltstock.
Claim 15
Dependent Claim
149 words
A process for producing a silicon ingot of large grain size multiple crystallinity suitable for use in photovoltaic cells from low purity silicon meltstock, said process comprising the steps of: a. providing a silicon meltstock having an impurity level greater than 10,000 ppm by weight; b. heating said silicon meltstock in a crucible to above its melting point; c. thereafter solidifying said melted silicon meltstock to product said ingot by extracting heat from the bottom of said crucible whereby impurity particles are excluded from the solidified meltstock forming the interior of said ingot subsequent to said heating and in the course of said solidifying and adhere loosely to the surface of the growing solid; and d. periodically, ii. rotating said solidifying melt in a first direction; and iii. thereafter decelerating the rotation of the meltstock sufficiently abruptly to dislodge said adhered impurities from the solidified portion of the meltstock.
Claim 16
Dependent Claim
13 words
The process of claim 13 wherein said adhered impurities are of silicon carbide.
Claim 17
Dependent Claim
20 words
The process of claim 14 where said silicon meltstock is metallurgical grade silicon produced by the carbothermic reduction of silica.
Claim 18
Dependent Claim
57 words
The process of claim 13 including the step of providing silica within said crucible prior to said solidifying, and wherein said impurities are removed from said meltstock by the step of reacting said silica with silicon carbide impurities in said silicon meltstock to cause the formation of reaction products that will separate from the melted silicon meltstock.
Claim 19
Dependent Claim
20 words
The process of claim 16 wherein before heating said silicon meltstock, said meltstock includes an adherent covering layer of silica.
Claim 20
Dependent Claim
24 words
The process of claim 16 wherein said silica is added to said melted silicon meltstock subsequent to said heating and prior to said solidifying.
Claim 21
Dependent Claim
42 words
The process of claim 13 including the step of reacting non-volatile impurities in said melt stock to form volatile impurities, and removing said volatile impurities from said silicon meltstock by reducing the pressure around said crucible to less than about 30 torr.
Claim 22
Dependent Claim
151 words
A process for producing a silicon ingot of substantially single crystallinity suitable for use in photovoltaic cells from low purity silicon meltstock, said process comprising the steps of: a. providing a silicon meltstock having an impurity level greater than 10,000 ppm by weight; b. heating said silicon meltstock in a crucible to above its melting point; c. thereafter solidifying said melted silicon meltstock to product said ingot by extracting heat from a central portion of the bottom of said crucible whereby impurity particles are excluded from the solidified meltstock forming the interior of said ingot subsequent to said heating and in the course of said solidifying and adhere loosely to the surface of the growing solid; and d. periodically, ii. moving said solidifying melt in a first direction; and iii. thereafter accelerating the motion of the meltstock sufficiently abruptly to dislodge said adhered impurities from the solidified portion of the meltstock.
Claim 23
Dependent Claim
151 words
A process for producing a silicon ingot of substantially single crystallinity suitable for use in photovoltaic cells from low purity silicon meltstock, said process comprising the steps of: a. providing a silicon meltstock having an impurity level greater than 10,000 ppm by weight; b. heating said silicon meltstock in a crucible to above its melting point; c. thereafter solidifying said melted silicon meltstock to product said ingot by extracting heat from a central portion of the bottom of said crucible whereby impurity particles are excluded from the solidified meltstock forming the interior of said ingot subsequent to said heating and in the course of said solidifying and adhere loosely to the surface of the growing solid; and d. periodically, ii. moving said solidifying melt in a first direction; and iii. thereafter accelerating the motion of the meltstock sufficiently abruptly to dislodge said adhered impurities from the solidified portion of the meltstock.
References Cited (Backward Citations)
No citation records indexed.
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