| 摘要 |
The present invention relates to a process for preparing polycrystalline silicon, in which a reaction gas comprising hydrogen and a silicon-containing gas are introduced into a reaction chamber and the silicon-containing gas is thermally decomposed over heated silicon and is deposited on the silicon to form an offgas and this offgas is separated into a first offgas fraction comprising trichlorosilane and chlorosilanes having a lower boiling point than trichlorosilane, and a second offgas fraction comprising components having a higher boiling point than trichlorosilane, and the first offgas fraction is supplied to the reaction gas of a deposition of polycrystalline silicon, and the second offgas fraction is separated into tetrachlorosilane and a high boiler fraction consisting of high boilers, with or without tetrachlorosilane, which comprises supplying the high boiler fraction to the reaction gas of a silicon deposition and heating the reaction gas to a temperature which ensures that the high boiler fraction is present in gaseous form on entry into the reaction chamber of the deposition reactor.
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