JPS5913618A - Method for purifying silicon tetrachloride - Google Patents

Abstract

PURPOSE:To obtain easily silicon tetrachloride contg. no impurity by purification by adding a nitrile compound represented by a specified rational formula to silicon tetrachloride contg. titanium tetrachloride as an impurity and by carrying out distillation. CONSTITUTION:A nitrile compound represented by a rational formula RCN (where R is a univalent org. group selected from alkyl, alkenyl, aryl and heterocyclic groups) is added to silicon tetrachloride to form a complex salt together with titanium tetrachloride contained in the silicon tetrachloride as an impurity, and after settling the complex salt as a precipitate, atmospheric distillation is carried out. The amount of the nitrile compound to be added is equal to or larger than the amount of the contained titanium tetrachloride, preferably about 4-10 times the amount by mole. CH3CN, CH2=CHCN or C6H5CN is especially suitable for use as the nitrile compound.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying silicon tetrachloride, and particularly to a method for removing titanium tetrachloride contained in silicon tetrachloride.

Silicon tetrachloride is obtained as a by-product of triglorosilane (5iHO1,) through the reaction of gold-containing silicon and hydrogen chloride, and is produced in large quantities as a by-product during the production of silicon for semiconductors by hydrogen reduction of triglosilane. It is well known that silica tetrachloride produced in this way is thermally decomposed or hydrolyzed in an oxyhydrogen flame to form fine silica powder, which is used in various industries. It is used either as a filler or as a raw material for manufacturing synthetic quartz.

<i/
Titanium tetrachloride (Ti014), which is a chloride of titanium titanium contained in silicon as an impurity, is unavoidably contained, and the amount of metallic titanium contained in silicon is unavoidable. It varies depending on the situation.

Usually several hundred PPI from filOPPb in silicon tetrachloride)
It is worshiped. And this titanium tetrachloride has a boiling point of 13
64°C, and the boiling point of silicon tetrachloride is 57.6°C. (1) Although most of silicon tetrachloride can be removed by distillation for the purpose of purification, Since the content is very small, this is IPPb.
It is difficult to achieve the following, and therefore, it is considered inevitable that fine particles of titanium tetrachloride are contained in fine silica powder and synthetic quartz made from this type of silicon tetrachloride.

Titanium oxide (Ti) produced from this titanium tetrachloride is contained in synthetic quartz produced from this silicon tetrachloride.
e,) is fixed, the transmittance of ultraviolet rays in the deep ultraviolet region is significantly reduced, resulting in the disadvantage that the ultraviolet transmittance, which is a characteristic of synthetic quartz, is reduced.For example, silicon tetrachloride as a raw material gas Contains 1 ppm of titanium tetrachloride.
If titanium tetrachloride is present, there is a disadvantage that the ultraviolet transmittance at 200 nm when this synthetic quartz is used as a mask substrate for fine ring raying is less than 1/3 of that when titanium tetrachloride is not present at all. Given.

The present invention relates to a method for refining silicon tetrachloride for the purpose of removing titanium tetrachloride, which can overcome such disadvantages, and this invention relates to a method for purifying silicon tetrachloride for the purpose of removing titanium tetrachloride.
(R is an alkyl group, an alkenyl group-aryl group,
The method is characterized in that a nitrile compound represented by a heterocyclic group (monovalent organic group selected from 1) is added, and then distilled.

To explain this, the present inventors have conducted various studies on methods for removing titanium tetrachloride present in silicon tetrachloride.
When a nitrile compound is added to silicon tetrachloride, this nitrile compound hardly reacts with silicon tetrachloride, but reacts selectively and easily with titanium tetrachloride at room temperature to form a complex, which produces a yellow color. After further investigation, we found that this complex does not decompose even at 57.6°C, which is the boiling point of silicon tetrachloride. The present invention was completed by confirming that silicon tetrachloride with a titanium content of ppb or less can be easily obtained.

Any type of silicon tetrachloride may be used as the treatment target in the method of the present invention, and there is no need to specifically limit it. Therefore, it may be obtained by a direct reaction between silicon and hydrogen chloride, or it may be a by-product during the production of silicon for semiconductors by hydrogen reduction of triglyceride.

Added to this silicon tetrachloride is a monovalent metallurgical group selected from the following formula RCN (wherein R is an alkyl group, an alkenyl group-aryl group, or a heterocyclic group). For example, acetonitrile (OH, ON), butyronitrile (OHs O
H! ON), butyronitrile COHa (O:Hz)
*Aliphatic saturated nitriles such as ON).

Aliphatically unsaturated nitriles such as agrilonitrile (OH,=CI!HON ), grotononitrile (OH,OH=OHON ), benzonitrile (0aHIION
), cinnamate nitrile [C・HIIOH= 0HO
Aromatic nitriles such as i/ampyridine (O
Examples include heterocyclic nitriles such as -ON). However, among these, it has good reactivity with titanium tetrachloride, the boiling point of the reaction product with titanium tetrachloride is as far as possible from the boiling point of silicon tetrachloride, it is less toxic, it is easy to handle, and it is safe. It is preferable that the material satisfies the conditions of being inert to metals and plastics, and furthermore being completely inactive to silicon tetrachloride. In particular, acetonitrile C is preferably selected.

2) The treatment of silicon tetrachloride with an IJ compound is
Since the reaction between these nitrile compounds and titanium tetrachloride proceeds at room temperature, it is only necessary to add this nitrile compound to silicon tetrachloride, which is liquid at room temperature, and stir it. The complex salt of the compound precipitates as a yellow precipitate in the tobacco liquid, so this silicon tetrachloride can be easily purified to be free of titanium tetrachloride by distilling it under normal pressure. In this case, addition 11 [1 of the nitrile compound]
The amount used must be at least the same molar amount as the molar amount of titanium tetrachloride contained in silicon tetrachloride before purification, preferably 3 to 10 times the molar amount. Good. In addition, the distillation after addition of the nitrile compound can be carried out using a metal, glass, or glass-lined distillation apparatus;
The operation may be carried out in a plate tower corresponding to plates under the conditions of a reduction ratio of 0.5 or more.

Next, Examples of the present invention will be given, in which the contents of titanium tetrachloride in silicon tetrachloride are all values measured by atomic absorption spectrometry.

Example 1 In 100 parts of silicon tetrachloride containing 1.0 ppm of titanium tetrachloride, 1 1 PPm of acetonitrile (OHs) corresponding to 5 times the molar amount of titanium tetrachloride was added.
ON) was added at room temperature, a yellowish brown precipitate was formed, which was then distilled at a reflux ratio of 0.5 in a 5-stage glass distillation apparatus. When we examined the titanium chloride-containing phase, we found that it was i P
It was below Pb.

Example 2

Claims (1)

[Claims] 1. Silicon tetrachloride is represented by the specific formula RON (where R is a monovalent organic group selected from an alkyl group, an alkenyl group, an aryl group - a hetea ring group) A method for purifying silicon tetrachloride, which comprises adding a nitrile compound and then distilling it. 2 2) Claim 1 in which the IJ compound is added in an amount equal to or more than the same mole of titanium tetrachloride contained in silicon tetrachloride.
Method for purifying silicon tetrachloride as described in Section 1. 3. The nitrile compound is acetonitrile (OHs ON
). 3. The method for purifying silica tetrachloride according to claim 1 or 2, wherein the method is selected from agrilonitrile (OH,=CHON) and benzonitrile (OgHllON).