Patent ID: 9238866
Filing Date: 2016-01-19
CPC Classification: C01B,C23C,Y10T

Claim Text:
1. A method for producing polycrystalline silicon rods having a rod diameter >100 mm, comprising: a) supplying a silicon-containing gas to a reactor containing silicon thin rods heated by electric power to a deposition temperature at which the silicon-containing gas deposits polycrystalline silicon onto the thin rods according to the Siemens process to form polycrystalline rods, increasing the diameter of the polycrystalline rods, and continuing supplying the silicon-containing gas at the deposition temperature until the diameter of the polycrystalline rods is >100 mm; b) ceasing the supply of silicon-containing gas and introducing hydrogen gas into the reactor at the deposition temperature, the hydrogen gas being introduced into the reactor at a pressure and at a flow rate such that the deposition temperature is maintained at a reduced power input which is ≧5 kW/m of rod length, and not less than 50% of the electric power of step a); and c) reducing the electric power and cooling the rods in the presence of hydrogen gas; and d) removing the rods from the reactor, wherein the rods removed from the reactor have cracks and/or radial stresses in an amount not less than 1·10