Patent ID: 8404205

Claim:
A method for manufacturing polycrystalline silicon having a reduced amount of boron compounds, comprising: reacting metallurgical silicon with hydrogen chloride to produce an unpurified trichlorosilane; distilling the unpurified trichlorosilane, wherein the distilling has a condenser for separating trichlorosilane from vapor fractions to form purified trichlorosilane; depositing polycrystalline silicon on silicon seed rods in a reactor by reducing and thermally decomposing the purified trichlorosilane by hydrogen reduction of trichlorosilane and thermal decomposition of trichlorosilane; purifying hydrogen discharged from the reactor in an activated carbon tower; mixing the vapor fractions from the condenser with a regeneration gas containing phosphorus compounds produced by the activated carbon tower, to form a mixture and combining the mixture with the unpurified trichlorosilane; feeding a mixture of the unpurified trichlorosilane, the regeneration gas, and the vapor fractions to the step of distilling the unpurified trichlorosilane, and removing high boiling point boron-phosphorus complex compounds as a residue fraction from the distilling step and separating trichlorosilane from vapor fractions.