METHODS FOR PURIFYING METALLURGICAL SILICON
First Claim
1. A method for purifying silicon bearing materials for photovoltaic applications, the method comprising:
- providing metallurgical silicon into a crucible apparatus;
subjecting the metallurgical silicon to at least a thermal process to cause the metallurgical silicon to change in state from a first state to a second state, the second stage being a molten state not exceeding 1500 Degrees Celsius;
causing at least a first portion of impurities to be removed from the metallurgical silicon in the molten state;
cooling the molten metallurgical silicon from a lower region to an upper region to cause the lower region to solidify while a second portion of impurities segregate and accumulate in a liquid state region;
solidifying the liquid state region to form a resulting silicon structure having a purified region and an impurity region; and
whereupon the purified region is characterized by a purity of greater than 99.9999%.
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Abstract
A method for purifying silicon bearing materials for photovoltaic applications includes providing metallurgical silicon into a crucible apparatus. The metallurgical silicon is subjected to at least a thermal process to cause the metallurgical silicon to change in state from a first state to a second state, the second stage being a molten state not exceeding 1500 Degrees Celsius. At least a first portion of impurities is caused to be removed from the metallurgical silicon in the molten state. The molten metallurgical silicon is cooled from a lower region to an upper region to cause the lower region to solidify while a second portion of impurities segregate and accumulate in a liquid state region. The liquid state region is solidified to form a resulting silicon structure having a purified region and an impurity region. The purified region is characterized by a purity of greater than 99.9999%.
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Citations
20 Claims
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1. A method for purifying silicon bearing materials for photovoltaic applications, the method comprising:
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providing metallurgical silicon into a crucible apparatus; subjecting the metallurgical silicon to at least a thermal process to cause the metallurgical silicon to change in state from a first state to a second state, the second stage being a molten state not exceeding 1500 Degrees Celsius; causing at least a first portion of impurities to be removed from the metallurgical silicon in the molten state; cooling the molten metallurgical silicon from a lower region to an upper region to cause the lower region to solidify while a second portion of impurities segregate and accumulate in a liquid state region; solidifying the liquid state region to form a resulting silicon structure having a purified region and an impurity region; and whereupon the purified region is characterized by a purity of greater than 99.9999%. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for purifying silicon for photovoltaic applications, the method comprising:
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providing metallurgical silicon into a crucible apparatus; subjecting the metallurgical silicon to at least a thermal process to cause the metallurgical silicon to change in state from a first state to a second state; causing at least a portion of impurities from being removed from the metallurgical silicon in the molten state; and maintaining the metallurgical silicon in a vacuum to selectively adjust a temperature of the molten state of the metallurgical silicon. - View Dependent Claims (16)
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17. A method for purifying silicon bearing materials for photovoltaic applications, the method comprising:
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providing metallurgical silicon into a crucible apparatus; subjecting the metallurgical silicon to at least a thermal process to cause the metallurgical silicon to change in state from a first state to a second state, the second stage being a molten state not exceeding 1500 Degrees Celsius; causing at least a first portion of impurities from being removed from the metallurgical silicon in the molten state; subjecting an upper molten region of the metallurgical silicon with an inert blanket of gas to prevent external impurities from contacting the metallurgical silicon in the molten state; and subjecting a portion of the upper molten region to a hydrogen gas to cause a reaction to cause removal of a boron impurity with the hydrogen gas. - View Dependent Claims (18, 19)
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20. A method for purifying silicon bearing materials for photovoltaic applications, the method comprising:
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providing metallurgical silicon having a purity of 99% into a crucible apparatus; and subjecting the metallurgical silicon to at least a thermal process to cause the metallurgical silicon to change in state from a first state to a second state, the second state of the metallurgical silicon including an inner portion having a temperature ranging from about 2500 to 3000 Degrees Celsius and an outer portion having an outer temperature not exceeding 1500 Degrees Celsius; and causing a convective current from a temperature differential between the inner portion and the outer portion of the metallurgical silicon.
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Specification