Abstract: A by-product mixture produced when polycrystalline silicon is deposited on a base material in a CVD reactor is made to react with chlorine to form a tetrachlorosilane (STC) effluent in a chlorination reaction vessel, and the tetrachlorosilane (STC) distillate is made to react with hydrogen in a hydrogenation reaction vessel to be converted into trichlorosilane (TCS). In the chlorination step, poly-silane contained in the above described by-product mixture can be efficiently recycled as a raw material for producing the polycrystalline silicon, which can enhance a yield of the production process. In addition, in the chlorination step, methyl chlorosilanes having boiling points close to TCS are hyper-chlorinated to be converted into hyper-chlorinated methyl chlorosilanes having higher boiling points, which facilitates the hyper-chlorinated methyl chlorosilanes to be separated into high concentration, and reduces carbon contamination of the polycrystalline silicon.

Abstract: The present invention includes a step of separating an effluent produced in a hydrogenation step of making tetrachlorosilane (STC) react with hydrogen into trichlorosilane (TCS), into a chlorosilane fraction containing a hydrocarbon and a TCS fraction, and a chlorination step of making the chlorosilane fraction containing the hydrocarbon react with chlorine to form STC and a substance containing a chlorinated hydrocarbon, wherein the effluent containing STC produced in the chlorination step is circulated to the hydrogenation step. In the chlorination step, the chlorosilane fraction containing a hydrocarbon (capable of containing hyper-hydrogenated chlorosilanes) having a boiling point close to TCS is hyper-chlorinated to be converted and acquire a higher boiling point, which facilitates the hyper-chlorinated chlorosilanes and the hyper-chlorinated hydrocarbons to be separated into high concentration, and increases the purity of TCS to be finally obtained.

Abstract: A hydrogenation reaction vessel makes STC-containing substance react with hydrogen to convert the substance into TCS. A low boils removal column separates a chlorosilane distillate discharged from a hydrogenation reaction vessel into TCS and a mixture distillate containing hyper-hydrogenated chlorosilane, and circulates the mixture distillate containing hyper-hydrogenated chlorosilane to the hydrogenation reaction vessel. The mixture distillate containing the hyper-hydrogenated chlorosilane separated in the low boils removal column is circulatingly supplied to the hydrogenation reaction vessel. Accordingly, low boils by-product conventionally wasted is circulated and recycled in the process, which results in enhancing a yield of TCS production.

Abstract: A by-product mixture produced in a process for producing polycrystalline silicon is made to react with chlorine to form tetrachlorosilane (STC) distillate in a chlorination reaction vessel, and the tetrachlorosilane (STC) distillate is made to react with hydrogen in a hydrogenation reaction vessel to be converted into trichlorosilane (TCS). In the chlorination step, methyl chlorosilanes having boiling points close to TCS are hyper-chlorinated to be converted into hyper-chlorinated methyl chlorosilanes having higher boiling points, which facilitates the hyper-chlorinated methyl chlorosilanes to be separated into high concentration, and inhibits carbon from contaminating the polycrystalline silicon. A donor/acceptor eliminator is provided in the circulation cycle for producing TCS, and accordingly there is no need to take out a by-product produced in the process for producing TCS to the outside of the system, which can highly purify the TCS.

Abstract: A vapor-phase growth plant which has a dopant gas supplying apparatus comprising a plurality of dopant gas supplying containers, and a multiple stage gas flow subsystem with a plurality of dopant gas supply conduits therein, of which said dopant gas supply conduits form a tournament-style network with a plurality of confluences on which the dopant gas supply conduits are united and the gas flows therein are merged for subjection to even mixing which results in gradual decreasing of the number of the dopant gas supply conduits as the dopant gas flows proceed in the multiple stage gas flow subsystem. Together with the equipped pressure reducing valves, the dopant gas which is highly evened in its pressure and its concentration can be supplied to the vapor-phase growth apparatus, thereby affording stable production of vapor-phase growth products with extremely lessened quality variance.

Abstract: The mixed gas of a liquid raw material is stably supplied to not only one reactor but also a plurality of reactors as maintained with high purity at a fixed concentration.

Abstract: A polycrystalline silicon rod for preparing a monocrystalline silicon rod by a floating zone method, wherein at least a central portion of the section of the polycrystalline silicon rod has coarsened silicon monocrystalline grains around the center over an area of or above the minimum section of a molten zone during progress in the floating zone method and the outer peripheral portion of the coarsened region has fine monocrystalline grains. From the polycrystalline silicon rod, the monocrystalline silicon rod for a semiconductor is prepared with a high yield by the single floating zone method.