Shin-etsu Chemical Co., Ltd.

Takeshi Aoyama

Tohru Kubota

Takaaki Shimizu

Yoichi Tonomura

Naruhiro Hoshino

Masahiko Ishida

Kyoji Oguro

Atsushi Yoshida

Shuji Tanaka

Masayuki Hasegawa

A polysilicon rod wherein in an area whose distance from a center of a cross section of the polysilicon rod is within ⅔ of a radius and that excludes a seed core, average grain boundary characteristics have following features: a coincidence grain boundary ratio exceeds 20%, a grain boundary length exceeds 550 mm/mm, and a random grain boundary length does not exceed 800 mm/mm.

Polysilicon rod and method for manufacturing polysilicon rod

The method comprises at least three steps of a hydrogenation step () and/or a chlorination step (), an impurity conversion step (), and a purification step (). In the impurity conversion step (), an aldehyde compound represented by the general formula Ar&#x2014;R&#x2014;CHO (Ar; denotes a substituted or unsubstituted aryl group, R; denotes an organic group having two or more carbon atoms) is added to convert donor impurities and acceptor impurities contained in a chlorosilane distillate to a high-boiling substance. The chlorosilane distillate after the donor impurities and acceptor impurities have been converted to a high-boiling substance is sent to the purification step (). In the purification step (), high purity chlorosilanes from which the donor impurities and acceptor impurities have been thoroughly removed are obtained by using a distillation column or the like, where the high purity chlorosilanes are recovered outside the system from the top of the column.

Method for purifying chlorosilanes

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.

Method for producing polycrystalline silicon

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Niigata, Japan

Takeshi Aoyama