A method and system for selectively recovering monochlorosilane and dichlorosilane from polysilicon production process are provided. The system and method selectively recover the monochlorosilane and the dichlorosilane contained in an exhaust stream discharged from a chemical vapor deposition unit for a polysilicon production process and the monochlorosilanes and the dichlorosilanes may be obtained with minimal capital investment or complexity.

Separation of chlorosilane mixtures containing boron, arsenic, and/or phosphorus impurities is facilitated by a distillative separation using at least one divided column, with recycle streams to a first column being passed through an external absorbent for the impurities.

[Problem] To provide a novel production method for pentachlorodisilane and to obtain pentachlorodisilane having a purity of 90 mass % or more by carrying out this production method. [Solution] A production method provided with: a high-temperature reaction step in which a raw material gas containing vaporized tetrachlorosilane and hydrogen is reacted at a high temperature in order to obtain a reaction product gas containing trichlorosilane; a pentachlorodisilane generation step in which the reaction product gas obtained in the high-temperature reaction step is brought into contact with a cooling liquid obtained by circulative cooling of a condensate that is generated by cooling the reaction product gas, the reaction product gas is quickly cooled, and pentachlorodisilane is generated within the condensate; and a recovery step in which the generated pentachlorodisilane is recovered.

The present invention relates to an apparatus and a method for producing polycrystalline silicon having a reduced amount of boron compound impurities. Especially, the boron compounds are removed from the process for producing polycrystalline silicon, while the trichlorosilane is purified by distillation. The invention feeds condensed liquid trichlorosilane into a primary distillation tower below the liquid level inside the primary distillation tower thereby scrubbing the boron impurities upon contact inside the primary distillation tower. There result is trichlorosilane leaving the primary distillation tower with total amount of boron at least 10 times less.

Methods for separating halosilanes that involve use of a distillation column having a partition that divides the column into portions for producing three product fractions are disclosed. Methods and systems for producing silane by disproportionation of halosilanes that use such columns and methods for producing polycrystalline silicon are also disclosed.

Efficient distillative separation of an at least three component mixture containing high boiler, medium boiler and low boiler components is accomplished by interposing a column having a stripping section and a rectifying section separated from each other by a horizontal impermeable dividing wall between conventional distillation columns. High efficiency and low capital cost is achieved.

There is provided trichlorosilane purification technology in which it is unnecessary to discharge large amounts of chlorosilanes oat of the system in the production of high-purity trichlorosilane from a chlorosilane fraction containing hydrocarbons and in which the reaction control can also be easily performed. In the present invention, the step of converting hydrocarbons contained in a chlorosilane fraction into low-boiling materials by thermal decomposition has been provided in the purification system in order to easily separate the hydrocarbons. Thereby, the conversion of hydrocarbons into low-boiling materials by thermal decomposition and the separation are performed in the trichlorosilane purification cycle, and it is unnecessary to discharge large amounts of chlorosilanes out of the system. As a result, the trichlorosilane production efficiency is increased, and the problem of yield reduction of polycrystalline silicon does not arise either.

The content of boron compounds in a composition containing at least one halosilane is reduced by bringing the composition into contact with at least one phenylsilane and removing the at least one halosilane. The invention further relates to the use of phenylsilanes for removing boron compounds from halosilane-containing compositions.

The invention relates to a process for removal of bromine, bromine- and/or iodine-containing silicon compounds from compositions of chlorosilanes containing bromine, bromine- and/or iodine-containing silicon compounds, wherein the composition is subjected to a nonthermal plasma and subsequently the chlorosilanes may be separated from the bromine- and/or iodine-containing compounds present by distillation.

Methods for purifying a halosilane-containing process stream include a process stream purified by removing arsenic and phosphorous impurities by use of distillation.