JP2001131187A - Purification method of monosilane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently purify monosilane by separating impurities in impurity gas-containing monosilane. SOLUTION: In a method for purifying monosilane obtained by disproportionating an alkoxysilane represented by the general formula HnSi(OR)1-n, n (wherein n is 1, 2 or 3; and R is an alkyl group or a cycloalkyl group) in the presence of a catalyst, impurity gas-containing monosilane is contacted with pure water to absorb the impurity gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compound represented by the general formula H _n Si
The present invention relates to a method for purifying monosilane obtained by disproportionating alkoxysilane having 1 to 3 hydrogen atoms represented by (OR) _4-n .

[0002]

2. Description of the Related Art Monosilane gas is widely used as a raw material for polycrystalline silicon, amorphous silicon, insulating films (silica), etc., for semiconductor substrates, solar cells, silicon epitaxial films, fine ceramics and the like. In addition, with the recent growth of the semiconductor industry, the demand has been rapidly increasing, and the development of a method for mass production at lower cost has been desired.

In the known monosilane production method, a production method by disproportionation of alkoxysilane is considered to be promising in view of mild reaction conditions and no generation of corrosive gas. A wide variety of studies have been made on catalysts and solvents for efficiently producing monosilane by this method. Further, in this method, since alkoxysilane is used as a raw material, there is an advantage that arsine, phosphine, and the like, which are problematic as impurity gases during conventional synthesis of monosilane, are not generated.

[0004] However, since hydrocarbons, which are considered to be caused by the alkyl group of the alkoxysilane, are generated in relatively large amounts as impurity gases, these must be separated. Generally, methods such as distillation and adsorption are used for separating hydrocarbons. However, the level of impurity gas in monosilane used as a semiconductor gas has a remarkable difference from a general level, and has a purity that cannot be reached by a distillation method utilizing a temperature difference. In addition, regarding the adsorption method which is considered to be effective as a method for removing a trace amount of impurity gas, there is a problem in that monosilane is also adsorbed to the adsorbent at the same time. In these methods, the amount of adsorption is reduced by ion exchange of zeolite, but this does not mean that the amount of adsorption of monosilane has become zero.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to purify monosilane efficiently by separating impurity gas from monosilane containing impurity gas produced by the alkoxysilane method while minimizing the amount of lost monosilane. It is to provide a method.

[0006]

Means for Solving the Problems The present inventors separate out impurity gas from monosilane containing impurity gas produced by the alkoxysilane method while minimizing the amount of lost monosilane, and purify monosilane efficiently. As a result of intensive studies on the method, it was found that as a separation and purification method, monosilane containing an impurity gas was brought into contact with pure water to achieve this purpose.

That is, the present invention relates to the general formula H _n Si (O
R) _4-n [where n is 1, 2 or 3 and R represents an alkyl group or a cycloalkyl group] disproportionation in the presence of a catalyst, and purification of the resulting monosilane The present invention relates to a method for purifying monosilane, comprising contacting and absorbing monosilane containing impurity gas with pure water.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Raw materials used in the present invention have the general formula H _n Si (OR)
_{4-n wherein} n is 1, 2 or 3, and R represents an alkyl group or a cycloalkyl group. Specific examples include, but are not limited to, trimethoxysilane, dimethoxysilane, triethoxysilane, diethoxysilane, and the like. Further, the composition does not necessarily have to be a single composition, and even if the composition contains tetraalkoxysilanes by-produced in the disproportionation reaction, no inconvenience occurs in the present invention, but a single composition is preferable. .

In the present invention, the catalyst used for the disproportionation reaction is used.
The medium is not particularly limited as long as monosilane can be obtained in high yield.
But the general formula MOH or M (OH)_Two[Where M is a
Indicates a rukari metal or an alkaline earth metal]
Metal hydroxide or a general formula MOR [where M is alkali gold
Genus or alkaline earth metal, wherein R is 1-6 carbon atoms
Represents an alkyl group or a cycloalkyl group of the formula]
Alkoxide or cobalt, nickel, or white metal gold
It is desirable to use a genus or a compound thereof. Specifically
Are lithium hydroxide, sodium hydroxide, potassium hydroxide
, Magnesium hydroxide, calcium hydroxide,
Lium, sodium Methoxide, sodium ethoxy
, Potassium methoxide, potassium ethoxide, NiF
_Four, CoF_TwoAnd the like.

The amount of the catalyst used may be such that the disproportionation reaction proceeds sufficiently efficiently and monosilane is generated efficiently, and generally 0.01 to 1% by weight based on the raw material alkoxysilane.
Is preferred. Since the reaction proceeds under relatively mild conditions,
Usually, 40 to 80 ° C. at normal pressure is preferred. Usually, it is preferable to perform the reaction under an atmosphere of an inert gas such as nitrogen.

In the disproportionation reaction in the present invention, the reaction can be carried out with or without a solvent, but it is more preferable to use it. Examples of the solvent used include tetraalkoxysilane, hexane, heptane and other aliphatic saturated hydrocarbons, and alicyclic saturated hydrocarbons such as cyclohexane and the like generated as by-products of the disproportionation reaction. When the reaction proceeds under the above conditions, monosilane containing an impurity gas is obtained by the disproportionation reaction. Therefore, by purifying the monosilane containing the impurity gas, high-purity monosilane can be obtained.

In the present invention, the purification of monosilane containing an impurity gas is carried out by bringing it into contact with pure water and absorbing it. Here, the pure water refers to water purified by desalting by distillation and then repeatedly distilled to obtain pure water, or water purified by an ion exchange resin. Monosilane usually does not react with or dissolve in pure water. On the other hand, although hydrocarbons have low solubility, they have solubility in water. Therefore, utilizing this difference, hydrocarbons are dissolved in pure water to purify monosilane. As a device used for contacting monosilane containing an impurity gas with pure water, a commonly used plate column, packed column, bubble column, spray column or the like can be used without any problem.

The pure water used in the present invention is preferably maintained at a constant pH value and temperature by circulating. Specifically, the pH value is preferably 6.90 to 7.10, and more preferably 6.95 to 7.05. It is preferable to adjust the temperature of contact with pure water to be 0 to 15 ° C, preferably 0 to 5 ° C. When the pH value is smaller than 6.90 or larger than 7.10, hydrolysis of monosilane occurs and the yield is undesirably reduced. On the other hand, if the temperature of pure water exceeds 15 ° C., the solubility of the impurity gas in pure water decreases, and the amount of impurity gas that cannot be separated increases, which is not preferable.

Using the raw materials, catalysts and solvents as described above, the monosilane containing the impurity gas obtained by the disproportionation reaction is brought into contact with pure water having a specific pH value and a specific temperature, so that the monosilane containing the impurity gas becomes The impurity gas contained can be separated and purified from monosilane.

[0015]

The present invention will be described below in detail with reference to examples. Example 1 0.05 g of potassium hydroxide as a catalyst and 60 g of tetramethoxysilane as a solvent were placed in a pressure-resistant glass container having a 200 ml internal volume equipped with a nitrogen gas inlet tube, a generated gas outlet tube, a raw material charging tube, and a solvent extraction tube. The mixture was charged and stirred with a magnetic stirrer, and the inside of the container was sufficiently replaced with nitrogen. The glass container was heated by a water bath to keep the solvent temperature at a constant temperature of 60 ° C. Thereafter, 60 g of trimethoxysilane was introduced from a liquid charging tube, and after the addition was completed,
The valve of the charging pipe was closed. In the reaction, monosilane was generated from the time when potassium hydroxide and trimethoxysilane came into contact. The generated monosilane was entirely collected in a stainless steel cylinder. The reaction was carried out for 3 hours, and after 3 hours, it was confirmed by gas chromatography (GC-8A manufactured by Shimadzu Corporation) that no monosilane was generated. As a result of measuring impurity gas (hydrocarbons) in monosilane, methane 20 ppm, ethane 11 ppm, propane, 6 pp
m, 4 ppm of butane and 7 ppm of ethylene were detected.
Thereafter, the collected monosilane gas was connected to a packed tower type absorption tower, and was passed through pure water adjusted to pH = 7.00 and a temperature of 3 ° C. under a normal pressure at a rate of 20 cc / min to wash the gas. When the gas at the outlet of the absorption tower was measured by gas chromatography (GC-FID, manufactured by Shimadzu Corporation), all hydrocarbons were below the detection limit.

Comparative Example 1 Monosilane containing an impurity gas synthesized in the same manner as in Example 1 was charged in an adsorption tower set at -80 ° C. with zeolite MS-.
5A was charged and connected, and allowed to flow at a rate of 20 cc / min under normal pressure. When the gas at the outlet of the adsorption tower was measured by gas chromatography, it was found that methane was 10 ppm and ethane was 0.5 ppm.
ppm, propane, 1 ppm, butane 1 ppm, and ethylene 0.5 ppm were detected.

[0017]

According to the purification method of the present invention, when monosilane containing an impurity gas is purified, the monosilane can be purified without loss, and the impurity gas can be separated with extremely high purity. Therefore, the industrial significance of the present invention is great.

Continued on front page F-term (reference) 4G069 AA06 BB05B BC03B CB41 DA02 4H039 CA92 CJ30 4H049 VN01 VP01 VQ21 VR44 VS21 VT03 VT23 VV01 VV20 VW09 VW36

Claims (3)

[Claims] 1. A general formula _{H n Si (OR) 4-} n [n wherein is 1, 2 or 3, R represents an alkyl group or cycloalkyl group] presence of a catalyst an alkoxysilane represented by A method for purifying a monosilane, comprising disproportionating under the following conditions, wherein the monosilane containing an impurity gas and pure water are contacted and absorbed. 2. A method for purifying monosilane, wherein the pure water has a pH of 6.90 to 7.10. 3. Contacting with monosilane containing impurity gas,
A method for purifying monosilane, wherein the temperature of pure water to be absorbed is 0 to 15 ° C.