Methods of recycling silicon swarf into electronic grade polysilicon or metallurgical-grade silicon
Methods of recycling silicon swarf into electronic grade polysilicon or metallurgical-grade silicon are described herein are described. In an example, a method includes cutting a silicon ingot and recovering silicon swarf having a first purity from the cutting process. The recovered silicon is purified in an upgraded metallurgical silicon process to produce electronic grade polysilicon particles having a second purity higher than the first purity. The upgraded metallurgical silicon process can include dissolving the recovered silicon particles in a molten aluminum metal smelt.
1. A method of purifying silicon, the method comprising:
subjecting silicon particles having a first purity to a silicon dioxide reduction operation to form a first product;
combining the first product with a hydrochloric acid source in a fluid bed reactor and expelling hydrogen gas at the fluid bed reactor to form trichorosilane;
subjecting the trichlorosilane to a dust filtration process;
subsequent to subjecting the trichlorosilane to the dust filtration process, subjecting the trichlorosilane to a trichlorosilane condensation process to form a second product;
distilling the second product to form purified trichlorosilane;
processing the purified trichlorosilane through a silicon evaporator and introducing hydrogen to form a third product; and
processing the third product through a chemical vapor deposition reactor to form silicon particles having a second purity greater than the first purity.
2. The method of claim 1 , wherein the first purity is metallurgical grade.
3. The method of claim 2 , wherein the second purity is electronic grade.
4. The method of claim 1 , wherein the second purity is electronic grade.
5. The method of claim 1 , wherein the second purity is greater than 10N.
6. The method of claim 1 , further comprising:
forming an ingot from the silicon particles having the second purity.
7. The method of claim 1 , wherein the silicon particles having the first purity include a p-type dopant.
8. The method of claim 1 , wherein the silicon particles having the first purity include an n-type dopant.
9. The method of claim 2 , wherein the first purity is less than 4N.