Primary distillation boron reduction

Patent metadata

Field	Value
Publication number	US-10294109-B2
Application number	US-201815872309-A
Country	US
Kind code	B2
Filing date	Jan 16, 2018
Priority date	Dec 1, 2014
Publication date	May 21, 2019
Grant date	May 21, 2019

Abstract

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.

First claim

What is claimed is:

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, boron compounds as impurities and other compounds, in a fluidized-bed reactor;
condensing the reacted gas to form a liquid containing trichlorosilane, boron compounds as impurities and other compounds;
feeding the liquid into a distillation unit below a liquid level inside the distillation unit;
distilling the liquid to separate the trichlorosilane from other compounds and to remove boron compounds impurities; and
using the trichlorosilane obtained from the distilling step to deposit 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 distillation unit has a low reflux ratio of <5 gpm.

3. The method for manufacturing polycrystalline silicon having a reduced amount of boron compounds according to claim 1 , wherein boron discharged from the distillation unit is less than about 40 ppm.

Assignees

• Mitsubishi Polycrystalline Silicon America Corp Mipsa
• Mitsubishi Materials Corp

Inventors

• Ashworth April
• Keevan Michael W

Classifications

• C01B33/035

  by decomposition or reduction of gaseous or vaporised silicon compounds in the presence of heated filaments of silicon, carbon or a refractory metal, e.g. tantalum or tungsten, or in the presence of heated silicon rods on which the formed silicon is deposited, a silicon rod being obtained, e.g. Siemens process · CPC title

• C01B33/10763

  from silicon · CPC title

• C01B33/039 Primary

  by conversion of the silicon into a compound, optional purification of the compound, and reconversion into silicon · CPC title

• C01B33/10778

  Purification · CPC title

• C01B33/021

  Preparation (chemical coating from the vapour phase C23C16/00) · CPC title