Method to convert waste silicon to high purity silicon
A process for the recovery of silicon includes providing silicon-containing solids recovered from a silicon manufacturing process, said recovered silicon-containing solids being substantially free of semiconductor dopants; converting the recovered silicon-containing solids into gaseous silicon forms; subjecting to purification by minimal distillation; collecting the gaseous silicon forms as a condensed liquid of silicon-containing compounds; and utilizing the silicon-containing compounds for silicon deposition.
1. A method of processing silicon-containing powder recovered from a silicon manufacturing process, the method consisting essentially of:
providing a high purity silicon powder recovered from a silicon manufacturing process-wherein said recovered high purity silicon powder has at least 99.999 wt % purity, less than 10 ppm metallic impurities, and has mean particle size of about 1-10 microns; converting the high purity silicon powder into trichlorosilane by a hydrochlorination reaction of said high purity silicon at a temperature of 200-250° C. by continuously providing a feed of a mixture of hydrogen chloride and hydrogen gases; and
separating the nonvolatile metal chlorides and process HCl and H 2 gases; and
performing no more than one distillation-purification step on the trichlorosilane prior to converting the trichlorosilane to solar grade silicon and performing at least one or no more than two distillation-purification steps on the trichlorosilane prior to converting the trichlorosilane to electronic grade silicon.
2. The method according to claim 1 , wherein the non-volatile metal chlorides are separated in a filter bed.
3. The method according to claim 1 , wherein the trichlorosilane is purified by one or two distillation processes to remove volatile impurities.
4. The method of claim 3 , wherein the one or two distillation processes to remove volatile impurities comprises separation of trichlorosilane from dichlorosilane and tetrachlorosilane.
5. The method of claim 1 , wherein the trichlorosilane purified using one or two distillation processes is decomposed in a silicon deposition process to deposit polysilicon or a silicon thin film.
6. The method of claim 1 , wherein the high purity silicon powder is a waste silicon byproduct of the silicon granule manufacturing process in fluid bed reactors or crushing high purity silicon chunks.
7. The method according to claim 1 , wherein said converting high purity silicon powder into trichlorosilane is performed primarily in a bed reactor.