Patent ID: 8685840

Claim:
An in-situ gettering method for removing metal impurities from the surface and interior of a upgraded metallurgical grade silicon wafer in a reaction chamber in a continuous manner including the steps of: cleaning the surface of the upgraded metallurgical grade silicon wafer including the steps of: providing the surface of the upgraded metallurgical grade silicon wafer with a first mixture of less than 5% hydrochloric acid gas with hydrogen carrier gas so that the hydrochloric acid gas mixture reacts with the metal impurities on the surface of the upgraded metallurgical grade silicon wafer and forms metal chloride; evaporating the metal chloride from the surface of the upgraded metallurgical grade silicon wafer at 1150Â° C.; and using the hydrogen carrier gas to remove the metal chloride from the surface of the upgraded metallurgical grade silicon wafer; forming a porous structure of silicon by etching the surface of the upgraded metallurgical grade silicon wafer with a second mixture of about 10% hydrochloric acid gas with hydrogen carrier gas at about 1000Â° C.; hot annealing the surface of the upgraded metallurgical grade silicon wafer in hydrogen carrier gas at temperature higher than 1000Â° C.; and removing the porous structure of silicon from the surface of the upgraded metallurgical grade silicon wafer by hot etching the surface of the upgraded metallurgical grade silicon wafer with a third mixture of more than 5% hydrochloric acid gas with hydrogen carrier gas at temperature higher than 1150Â° C.