JPS61191512A - Production of disilane - Google Patents

Abstract

PURPOSE:To produce safely disilane in a high yield without requiring cooling to an extremely low temp. by reducing hexachlorodisilane with a metallic hydrogen compound in a specified boiling solvent. CONSTITUTION:A metallic hydrogen compound such as LiAlH4 is added to sufficiently dehydrated diethyl ether and/or diisopropyl ether as a solvent by an amount (weight) 1-10 times the amount of hexachlorodisilane to be added and the solvent is kept in a boiling state. Hexachlorodisilane is slowly added to the boiling solvent under ordinary or elevated pressure in 3-10hr, and disilane produced by reduction is introduced into a soubleor multi-tube type condenser, condensed, and collected in a vessel kept cold. Thus, disilane useful as a special gas for producing a silicon semiconductor can be produced in a high yield.

Description

[Detailed Description of the Invention] (a) Purpose of the Invention [Field of Industrial Application] The present invention has been evaluated for its high-speed film-forming properties, low-temperature film-forming properties, etc., as a special gas for manufacturing silicon-based semiconductors, etc. There is a method for producing disilane, for which demand is expected to increase dramatically in the future.

[Conventional technology]

As a known technique for producing disilane by reducing hexachlorodisilane with a metal hydride, for example, JP-A-58
There is a bud described in the publication No.-156522. This is a method for obtaining disilane by reducing a disilane derivative such as hexachlorodisilane in a solvent, in which the reaction is carried out at normal pressure or under pressure, and an inert gas is blown into the reaction solution heated to 10 to 80°C. This feature is characterized in that disilane dissolved in the solvent is separated by immersing it in the solvent.

[Problem that the invention seeks to solve]

As mentioned above, when the disilane produced by the reduction reaction and remaining dissolved in the solvent is separated by being diffused by blowing in a large inert gas, the partial pressure of disilane is lowered by the inert gas. Therefore, extremely low temperatures are required to collect disilane, which not only increases the cost of cooling, but also results in a large proportion of losses due to uncollected disilane.

That is, when using a refrigerator to cool an inert gas containing disilane and condensing the disilane, the current limit is -70 to -90°C even for cryogenic refrigerators, and lower temperatures are required. When cooling is required, it is common to use the latent heat of vaporization of liquid nitrogen, which is extremely expensive.

On the other hand, the vapor pressure of Dishoran at low temperature is approximately as shown in the table below. Temperature (℃) Vapor pressure (IIIH, 9) - 608
8゜0 -70 47.7 -80 24.1 -90 11.1 -100 4.7 -110 1.7 When disilane is expelled from the solvent by blowing inert gas, disilane is diluted by the inert gas. , the disilane concentration in the gas is almost on the order of a few percent (single digits), and ranges from -70 to
At temperature levels of -90°C it is difficult to condense basolateral disilane. Therefore, it is essential to cool it to an extremely low temperature of at least -100° C. or lower, which increases utility costs.

If liquid nitrogen is used, it can be cooled down to its boiling point of -196°C under normal pressure, so the idea that there is no problem in collecting disilane even if it is diluted with an inert gas is extremely dangerous for the following reasons. .

First of all, the melting point of disilane is -132.5°C,
When condensing disilane diluted with an inert gas, if the temperature is lower than that, the disilane will become solid and there is a risk of blockage.

Next, disilane (although the same is true for monosilane)
The reason for this is the fact that disilane does not change when it comes into contact with air in its solid state at temperatures below its melting point, but when it heats up and becomes liquid it causes an extremely violent explosion. The fact is that even if air is supplied to the reappointment area, combustion will occur, but no explosion will occur. These facts were discovered as a result of explosion experiments conducted by the present inventors using extremely small amounts of disilane, but they do mean that the presence or absence of an explosion varies depending on the cooling temperature level. This is a matter that should be given due consideration when handling disilane.

However, when condensing disilane from diluted disilane in the method of blowing inert gas, it is necessary to cool it to at least 1100°C or below, but not to below 1130°C due to the above-mentioned problems. It is hoped that

However, the reality is that there is no good method for cooling in the range of -100 to -130°C.

Although it is not impossible to control the temperature between -100 and -160℃ using liquid nitrogen, it is inefficient, and there is also a possibility that the temperature may be lowered to below -130℃ due to incorrect operation. Even when handling materials, it is extremely difficult to completely eliminate contact with air.

When producing disilane, the present inventors believe that the method of reducing hexachlorodisilane has a good yield and is the most suitable as an industrial production method.This method solves the above problems and is safe and has a high yield. The present invention was completed as a result of intensive research into a method for economically obtaining disilane.

(B) Structure of the Invention [Means for Solving Problems] The present invention provides a method for producing disilane by reducing hexachlorodisilane with a metal hydride in a solvent, in which diethyl ether or/and diisopropyl ether is used as the solvent. This is a method for producing disilane, characterized in that the reaction is carried out under pressure or under increased pressure in a boiling state of the solvent.

Although hexachlorodisilane produced by any method can be used, it is usually obtained by chlorinating a silicon alloy and separating impurities from the by-produced silicon tetrachloride and octachlorodisilane.

Examples of the metal hydride include lithium aluminum hydride, sodium aluminum hydride, lithium hydride, diethyl aluminum hydride, and the like.

In the present invention, the ratio of metal hydride to hexachlorodisilane to be supplied to the reaction system is the ratio (theoretical composition) required to replace all the chlorine in hexachlorodisilane with hydrogen.
is 1.0, preferably 0.95 to 1.30,
Furthermore, the amount of metal hydride is slightly excessive 101 to 1.20
It is preferable that If Q is less than 95, the proportion of chlorine-containing silane gas may increase, and if it exceeds t30, the yield of disilane will not increase and the cost will increase, which is not preferable.

Diethyl ether and diisopropyl ether used as solvents may be used alone or in a mixture thereof.

Furthermore, it is also possible to use a solvent that is a mixture of diethyl ether and/or diisopropyl ether with other solvents, and in that case, the other solvent used must have a boiling point of the mixed solvent of 80°C or less. Ru. If the boiling point of the mixed solvent exceeds 80°C, the yield of disilane will decrease, which is not preferable.

Note that these solvents should be sufficiently dehydrated.

The feed ratio of diethyl ether and/or diisopropyl ether (hereinafter simply referred to as ether solvent) to the reaction system varies slightly depending on the metal hydride used, but
The it ratio is preferably 1 to 10 times based on hexachlorodisilane. If it is less than 1 times, the slurry concentration of metal hydride and reaction product may increase, and if it exceeds 10 times, the volume ratio may substantially decrease.

When supplying hexachlorodisilane, a metal hydride, and an ether solvent to a reaction system, for example, the metal hydride is dissolved or suspended in an ether solvent, and while stirring thoroughly, hexachlorodisilane is added alone or diluted with an ether solvent. Generally, this is done by adding

As mentioned above, the pressure during the reaction is important from the standpoint of safety and operability, and in order to operate under reduced pressure, special equipment is required to prevent air from entering the system, which increases equipment costs. Therefore, it is carried out under normal pressure or increased pressure, but it is not necessary to use a very high pressure; near normal pressure is sufficient.

In the present invention, the reaction should be carried out in the boiling state of the solvent. By carrying out the reaction in this boiling state, the generated disilane is expelled from the reaction system in a highly concentrated state by the vapor of the solvent and is collected.

To carry out the reaction in the boiling state of the solvent, first warm the reaction system to the boiling point of the solvent, reflux the ether solvent in a condenser attached to the top of the reactor, and then start the reaction. Alternatively, since this reaction is an exothermic reaction, the reaction heat can be used to bring the reaction to a boiling state and carry out the reaction. Since the temperature of the reaction solution decreases after the reaction is completed, it is preferable to completely expel the generated disilane by heating it for a while and refluxing the ether solvent. Reactions in the boiling state of ether solvents have the advantage of being very easy to control the reaction temperature and requiring simple equipment.

The reduction rate of hexachlorodisilane is extremely fast and the heat of reaction is extremely large. Therefore, the rate of supply of hexachlorodisilane to the reaction system is determined by the capacity of the reflux condenser, etc., but it is usually supplied slowly over a period of 3 to 10 hours to maintain the boiling state of the solvent at an appropriate level.

The condenser at the top of the reactor may be cooled to such an extent that the ether solvent is refluxed, and a small amount of ether solvent vapor may be transferred to the next collection step along with the disilane gas. It is also a desirable embodiment to install a rectification column between the reactor and the reflux condenser to improve the separation accuracy of the ether solvent and disilane. Condense it and collect it in a refrigerated container, or collect it in a trap type. Disilane gas separated from the reaction system contains hydrogen and mono-7 produced as by-products in the reaction.
It contains a small amount of inert gas that was initially replaced in the system, has a high concentration, and can be obtained using a cryogenic refrigerator.
Fruit thinning can be achieved with a sufficiently high yield using a refrigerant at a temperature of about 0 to -90°C.

Furthermore, by further refining the disilane obtained by the method of the present invention by a normal rectification operation, it is possible to remove trace amounts of impurities such as monosilane, trisilane, ether, and hydrocarbons, and it can be used as a semiconductor raw material. High purity disilane can be obtained.

[Examples and comparative examples]

Next, the present invention will be concretely illustrated using Examples and Comparative Examples, but the technical scope of the present invention is not limited thereto.

Example 1 A 5J jacketed SUS reactor equipped with a stirrer, a liquid supply port, a reflux condenser, and a thermometer protection tube was used. A metering pump was read directly to the liquid supply port to quantitatively supply hexachlorodisilane. The reflux condenser is a double pipe type filled with a Raschig ring.
It was cooled in a -10°C prine. Following the reflux condenser, a disilane trap cooled to -78°C with dry ice-methanol was read directly, and a small amount of nitrogen gas was passed through the pipe after the trap, leading to the abatement device via a water seal tank.

In addition, a vacuum pump was installed so that the entire apparatus could be replaced with an inert gas, and the vacuum operation and inert gas introduction operation were repeated, and the airtightness of the entire apparatus was confirmed.

After charging LiAgH42001 into a reactor and purging the system with nitrogen gas, thoroughly dried diethyl ether 1
J was added dropwise and stirred. Next, the reactor was heated, and after the reflux of diethyl ether started, a mixture of hexachlorodisilane 858 @ and diethyl ether 1J was added dropwise using a metering pump over 4 hours to cause a reaction. The reaction temperature was constant at the boiling point of diethyl ether under normal pressure. After the hexachlorodisilane mixture was added dropwise, stirring and refluxing of diethyl ether were continued for 1 hour to completely expel the disilane.

The disilane in the trap was transferred to a cylinder, and the weight and purity of the disilane were analyzed, and the concentration of disilane was 174I. The disilane yield was 88% based on hexachlorodisilane.

Example 2 Using the same reaction apparatus as in Example 1, a reaction was carried out using diisopropyl ether as a solvent.

LiA6H, 2001 and diisopropyl ether 11 were charged and heated to the boiling point of diisopropyl ether by flowing hot water at 70°C into the reactor jacket while stirring.

Next, a mixture of 857 I hexachlorodisilane and 1.5 l of diisopropyl ether was added dropwise over 5 hours using a metering pump, and the diisopropyl ether was allowed to react while being refluxed. Even after the dropwise addition, stirring and heating were continued to drive out the disilane. Ta. Eviction time was 1 hour.

The yield of disilane was 16B&, and the yield based on hexachlorodisilane was 85%.

Comparative Example Using the same reactor as in Example 1, tetrahydrofuran (T
) IF) was used as a solvent.

LiAJ Nagi-00g and THFl were charged, and hot water at 70°C was poured into the reactor jacket while stirring, and the temperature was raised to the boiling point of THF. Then 858g of hexachlorodisilane
A mixed solution of 5 and THFt was added dropwise over 5 hours using a constant voltage boss, and reacted while refluxing the THF. Refluxing was continued for 1 hour even after the dropwise addition was completed to completely expel disilane.

Very little charge was collected in the trap cooled to -78°C, of which disilane was only 18.21% yield 92%.
).

Analysis of the trap exhaust gas revealed that a large amount of monosilane was produced.

(c) Effects of the Invention According to the present invention, when producing disilane by reducing hexachlorodisilane, it is possible to separate disilane from the anti-core system in a highly concentrated state without diluting it with an inert gas, Therefore, extremely low-temperature cooling is not required, disilane can be obtained safely and in high yield using a cryogenic refrigerator, and the equipment is simple and economically advantageous.

Claims (1)

[Claims] 1. In a method for producing disilane by reducing hexadichlorosilane with a metal hydride in a solvent, diethyl ether or/and diisopropyl ether is used as the solvent, and the reaction is carried out at the boiling state of the solvent under normal pressure or increased pressure. A method for producing disilane, characterized by the following.