High purity crystalline silicon, high purity silicon tetrachloride for processes for producing the same
View Patent ↗An object of the present invention is to provide more inexpensive high purity crystalline silicon which can satisfy not only a quality required to a raw material of silicon for a solar cell but also a part of a quality required to silicon for an up-to-date semiconductor and a production process for the same and provide high purity silicon tetrachloride used for production of high purity crystalline silicon and a production process for the same. The high purity crystalline silicon of the present invention has a boron content of 0.015 ppmw or less and a zinc content of 50 to 1000 ppbw. The production process for high purity crystalline silicon according to the present invention is characterized by that a silicon tetrachloride gas and a zinc gas are supplied to a vertical reactor to react them at 800 to 1200° C., whereby crude crystalline silicon is formed at a chip part of a silicon tetrachloride gas-supplying nozzle, and the crude crystalline silicon is grown downward from the chip part of the silicon tetrachloride gas-supplying nozzle; the grown crude crystalline silicon is discharged to an outside of the reactor, and the discharged crude crystalline silicon is subjected to acid treatment.
1. A production process for high purity crystalline silicon, which is a process for producing a high purity crystalline silicon having a boron content of 0.015 ppmw or less and a zinc content of 50 to 1000 ppbw, comprising:
(1) a step in which in a vertical reactor equipped with a silicon tetrachloride gas-supplying nozzle, a zinc gas-supplying nozzle and a waste gas-discharging pipe, the silicon tetrachloride gas-supplying nozzle being inserted into an inside of the reactor from an upper part thereof and set therein, a silicon tetrachloride gas is supplied from the silicon tetrachloride gas-supplying nozzle and a zinc gas is supplied from the zinc gas-supplying nozzle,
(2) a step in which the silicon tetrachloride gas is reacted with the zinc gas at 800 to 1200° C. to thereby form crude crystalline silicon at a chip part of the silicon tetrachloride gas-supplying nozzle,
(3) a step in which the crude crystalline silicon is grown downward from the chip part of the silicon tetrachloride gas-supplying nozzle,
(4) a step in which the grown crude crystalline silicon is discharged to an outside of the vertical reactor and
(5) a step in which the discharged crude crystalline silicon is subjected to acid treatment,
wherein high purity silicon tetrachloride having an organic silicon compound content of 0.1 ppmw or less and a boron content of 0.1 ppbw or less is used as a raw material of the silicon tetrachloride gas, and metal zinc having a purity of 99.99% by weight or more is used as a raw material of the zinc gas.
2. The production process for high purity crystalline silicon of claim 1 , wherein the step (5) comprises a step for crushing the discharged crude crystalline silicon, a step for subjecting the crushed crude crystalline silicon to acid treatment, a step for washing the acid-treated product and a step for drying the washed product.
3. The production process for high purity crystalline silicon of claim 1 , wherein the step (5) comprises a step for subjecting the crude crystalline silicon crushed to a particle diameter of 0.1 to 5 mm to acid treatment and a step for washing the acid-treated product with purified water.
4. The production process for high purity crystalline silicon of claim 2 , wherein the step (5) comprises a step for subjecting the crude crystalline silicon crushed to a particle diameter of 0.1 to 5 mm to acid treatment and a step for washing the acid-treated product with purified water.