Apparatus and method for producing polycrystalline silicon having a reduced amount of boron compounds by venting the system with an inert gas
The invention concern an apparatus and a method for manufacturing polycrystalline silicon having a reduced amount of boron compounds. The invention feeds Ar gas in a trichlorosilane line, which connects a trichlorosilane (TCS) tank and a series of distillation units. The distillation units have a pressure transducer and a pressure independent control valve (PIC-V) positioned on a vent gas line for discharging vent gas from the distillation units. Ar gas is fed to the TCS line with higher pressure than the pressure set for opening the PIC-V. The TCS is distilled by the distillation units with continuously discharging vent gas from the distillation units.
1. A method for manufacturing polycrystalline silicon having a reduced amount of boron compounds, comprising:
reacting metallurgical grade silicon with hydrogen chloride to produce a reacted gas, including trichlorosilane, in a fluidized-bed reactor;
feeding an inert gas from an inert gas feeding unit to a line extending from the fluidized-bed reactor to a distillation unit, the line containing the reacted gas including trichlorosilane;
distilling the trichlorosilane while continuously discharging a vent gas from the distillation unit; and
reducing the resulting distilled trichlorosilane with hydrogen to produce polycrystalline silicon and depositing the polycrystalline silicon on silicon seed rods.
2. The method for manufacturing polycrystalline silicon having a reduced amount of boron compounds according to claim 1 , wherein the inert gas is Ar gas.
3. The method for manufacturing polycrystalline silicon having a reduced amount of boron compounds according to claim 1 , wherein trichlorosilane after distillation is purified to less than about 0.030 ppbwt of boron compound.