Patent ID: 8507051

Claim:
A polycrystalline silicon producing method comprising: supplying electric current to a silicon seed rod in a reactor to make the silicon seed rod to generate heat; supplying raw material gas including chlorosilanes to the silicon seed rod; and depositing polycrystalline silicon on a surface of the silicon seed rod to be grown as a rod, wherein a pressure in the reactor is equal to or greater than 0.4 MPa and equal to or less than 0.9 MPa, the method includes a first process and a second process, in the first process, a surface temperature of the rod is maintained at a predetermined range by adjusting the current value in the silicon seed rod, and the raw material gas is supplied while maintaining a supply amount of chlorosilanes per square millimeter of the surface of the rod to be equal to or greater than 2.0×10 -7 mol/sec/mm 2 and equal to or less than 3.5×10 -7 mol/sec/mm 2 until a temperature of the center portion of a rod reaches a predetermined temperature lower than the melting point of the polycrystalline silicon, and in the second process, after the temperature of the center portion of the rod reaches a predetermined temperature lower than the melting point of the polycrystalline silicon, a previously determined current value is set corresponding to a rod diameter and the supply amount of the raw material gas per square millimeter of the surface of the rod is decreased to maintain the surface temperature and the temperature of the center portion of the rod to be within predetermined ranges, respectively.