Patent ID: 8409319

Claim:
A silicon purification method comprising a solidification purification step in which metal impurities are removed by irradiating a base material made of metallic silicon with an electron beam, the solidification purification step comprising: (A) preparing the base material to be purified at one time, loading a part of the base material into a water-cooled crucible, irradiating, with the electron beam, the entire area of a part of the loaded base material that is disposed under a high vacuum atmosphere, and thereby fully melting the part of the base material; (B) gradually solidifying a molten part of the base material from a molten metal bottom thereof toward a molten metal surface thereof by gradually weakening an output of the electron beam so that the solidification proceeds until the solidifying portion occupies a first predetermined ratio of the total of the base material; (C) further loading a remnant of the base material into the water-cooled crucible, and fully melting the remnant of the base material by irradiating the entire area of the remnant of the base material with the electron beam; (D) gradually solidifying a molten metal portion from a bottom thereof toward a molten metal surface thereof by gradually weakening an output of the electron beam so that the solidification proceeds until the solidifying portion occupies a second predetermined ratio of the total of the molten metal portion; and (E) removing an unsolidified molten metal portion, wherein the (A) to (E) is performed in this order.