JPS58156522A - Preparation of disilane - Google Patents

Abstract

PURPOSE:To prepare a disilane of high purity in high yield in reducing a disilane derivative with a metallic hydride in a solvent to prepare the disilane, by carrying out the reducing reaction at a specific temperature while blowing an inert gas through the reaction system. CONSTITUTION:A disilane derivative, e.g. hexachloridisilane, dichlorodisilane or trichlorodisilane, is introduced into an autoclave, and a metallic hydride, e.g. LiAlH4 or sodium aluminum hydride, as a reducing agent is then suspended or dissolved in a solvent, e.g. n-butyl ether or tetrahydrofuran, introduced into the autoclave and mixed with the disilane derivative. The reaction is then carried out at 10-80 deg.C while blowing an inert gas, e.g. H2, He, Ar or N2, through the reaction system under ordinary or higher pressure. The aimed disilane of high purity containing substantially no disilylmethane as an impurity is obtained in high yield.

Description

[Detailed description of the invention] Concerning a new method for efficient manufacturing.

More specifically, this is a new method that overcomes the drawbacks of conventionally known methods for producing disilane by reducing a disilane derivative with a metal hydride.

Conventionally known methods for synthesizing disilane include the glow discharge method using monosilane as a raw material, the direct hydrogenation method of metal silicon, and the water decomposition method of calcium silicide and magnesium silicide, but all of them have various drawbacks. .

Particularly serious problems are that, in addition to the target disilane, a large amount of monosilane, trisilane, and other higher silanes are produced as by-products, resulting in a low yield of disilane, and that it is difficult to separate the target product. It is very dangerous to operate because it is easy to disassemble.

The method of synthesizing disilane using a disilane derivative having a Si-Si skeleton as a starting material from the boiled-down process is very superior in that it produces few by-products of monosilane and high-grade silane, and is suitable for mass production of disilane and disilane. There is.

As a conventionally known method for synthesizing disilane using a disilane derivative as a starting material, hexachlorodisilane (hereinafter 8i2C/s (!: shown)) is used as a disilane derivative.
Using A. E. Pinholt et al.
(J, A.C.8.

69 2692 (]947)) was improved.

, wBethke et, al4J, C. P. 26
No. 5 107 (1958):).

(D Technological Technique) Disilane is obtained by reducing Si2Cla with lithium aluminum hydride (hereinafter referred to as L i A/H4), but the reduction reaction is performed in vacuum.

However, disilane is self-flammable in the air, so keeping a sealed container such as a tank or autoclave in which disilane is handled in a vacuum poses a high risk of air getting in, which could lead to an explosion. cause.

If this risk were to be avoided, the manufacturing equipment would become extremely expensive.

Therefore, it became imperative to establish a safe manufacturing method under normal pressure or increased pressure.

By the way, disilane is a gas with a boiling point of 115°C.
It is highly soluble in various organic solvents.

When disilane is produced by a reduction reaction using such a solvent, only a small amount of disilane can be obtained directly as a gas, and most of it remains in the solvent. As a result, the actual yield decreases. In order to improve this point, even if disilane is separated from the solvent under reduced pressure, it takes a very long time to recover the produced disilane in a good yield due to the high solubility of disilane.

Another method for separating gases in a solvent is to heat the solvent to near its boiling point, but this method results in large amounts of impurities present in the solvent being entrained in the disilane.

In particular, disilane for semiconductor manufacturing must be free of impurities as much as possible. In particular, carbon compounds serve as carbon sources in semiconductors, significantly deteriorating their performance.

By the way, by reducing a disilane derivative with a metal hydride,
In the reaction to obtain disilane, disilylmethane (hereinafter S
It is designated as iH-CHt-8iHs. ) is generated. This compound does not exhibit selective adsorption characteristics with disilane on activated carbon or synthetic zeolite, which are often used to purify impurities.

As a result, purification of disilane containing 5iHs-CH-8iHs is not an easy task.

As a result of intensive studies taking the above points into consideration, we have arrived at the present invention which eliminates the above problems.

That is, the present invention provides a method for obtaining disilane by reducing a disilane derivative in a solvent. This method is characterized in that it is obtained by separating it from a solvent.

According to the method of the present invention, disilane can be obtained safely and in high yield, and in particular, is substantially free of 5iHs-CH-8iHs as an impurity.

The present invention will be explained in more detail below.

The disilane derivative used as the raw material for producing disilane is 8i −
General formula 8itHnX@-n (n
A positive number from -0 to 5. X is a chloro group or an ethoxy group. ).

Specific examples include hexachlorodisilane, dichlorodisilane, trichlorodisilane, tetrachlorodisilane, yoxaethoxydisilane, and tetrachlorojethoxydisilane. Among these, hexachlorodisilane is particularly preferred since it is easily available.

Hexachlorodisilane may be produced by any method, but it is preferably one that does not contain impurities such as silicon tetrachloride and octachlortrisilane.

The disilane derivative is used as it is or as a solution.

A metal hydride is used as a reducing agent for the disilane compound. For example, LiA/H4, sodium aluminum hydride, diethyl aluminum hydride, etc. are preferred.

These are used as solutions or suspensions.

The reduction reaction is carried out in a solvent, and suitable choices for each reducing agent can be made.

For example, LiA/Ha includes n-butyl-nithyl,
Ethers such as tetrahydrofuran and diethyl ether are preferably used. In addition to the above-mentioned ethers, for diethylaluminium hydride, saturated hydrocarbons such as heptane, octane, and fluidized crude oil, and aromatic hydrocarbons such as toluene and benzene can be used.

It is preferable that the boiling point of these reaction solvents is higher, since the amount entrained in disilane during injection of active gas after the reaction is reduced. The solvent is sufficiently dehydrated and replaced with an inert gas to be used later.

The order in which the disilane derivative and metal hydride are added to the reaction solvent during reduction may be either adding the disilane derivative to the solution of the metal hydride or vice versa. do not have.

The temperature for the reduction reaction is selected keeping in mind the progress of the forward reaction and the suppression of side reactions.

As mentioned above, the pressure state during reduction is normal pressure or elevated pressure from the viewpoint of safety and economic efficiency, but it is not necessary to use a particularly high pressure, and a pressure close to normal pressure is sufficient.

In the prior art, reduction of disilane was carried out under reduced pressure. This seems to be due to considerations for convenient recovery of the produced gas. As a result of our research, we learned that the reduction reaction according to the present invention will proceed in the positive direction with a high reaction rate under the conditions specified in the claims. Therefore, the method of recovering disilane dissolved in the reaction solvent was chosen, and this method is based on an excellent idea that is not an extension of conventional common sense.

During the reduction reaction, most of the disilane remains in the solvent, but some disilane is liberated as a gas.

This is collected in a cold trap connected to the reaction vessel.

Next, a process of recovering disilane in the solvent by blowing inert gas after the reduction reaction will be described.

The inert gas may be any gas that does not react with the raw material or the reduction reaction product and is easily separated from disilane. For example, hydrogen, helium, argon, and nitrogen.

These gases are also sufficiently dehydrated or deoxidized to remove impurities before use.

The method for blowing inert gas may be, for example, using a dip pipe attached to the reaction vessel. To improve the dispersion of inert gas,
A porous plate or a diffusion plate may be used, or the inside of the reaction vessel may be stirred.

The amount of inert gas used is sufficient to entrain all the disilane in the solvent, but this amount is largely controlled by the temperature of the solvent, the structure of the equipment, and the flow rate of the inert gas. .

The temperature inside the container during inert gas injection must be below the boiling point of the solvent used during the reaction, but if it is too high even within that range, 8iHs-CH*-8iHs will be entrained, which is undesirable, and the If it is too low, the effect of separating disilane from the solvent will be poor and the time for blowing inert gas will become long, which is not preferable. However, a range of 10°C to 80°C is sufficient, and preferably a range of 30°C to 70°C.

The pressure at which the inert gas is blown must be normal pressure or increased pressure; however, even if the pressure is particularly high, there is no particular effect, and a pressure close to normal pressure is sufficient.

Note that when blowing inert gas, it is sufficient to use a reduction reaction container, but if you transfer the solution after the reduction reaction to another container,
You can also inject it into that.

As a method for separating and recovering disilane entrained in the inert gas, for example, a cooling trap is used.

This temperature may be below the temperature corresponding to the vapor partial pressure of disilane at that time and above the boiling point of the inert gas. In this way, disilane is liquefied or solidified and separated from the inert gas.

Further, it is preferable to provide a cooling trap in front of the disilane recovery cooling trap for removing the reaction solvent entrained in the inert gas together with disilane.

Note that if the disilane obtained by the method of the present invention is to be further purified, it is first passed through an activated carbon layer to remove trace amounts of remaining solvent and chlorinated substances derived from raw materials or reduction reactions, and then purified with synthetic zeolite. It is possible to remove trace amounts of hydrocarbons such as methane and ethane.

In this way, it is possible to obtain highly purified disilane containing only a very small amount of monosilane and trisilane, which have almost no effect, by using disilane as a raw material for semiconductor production.

Furthermore, monosilane 1 and trisilane can also be removed by simple distillation.

Next, the present invention will be illustrated with specific examples, but the technical scope of the present invention, which can be easily understood from the above description, is not limited thereto.

(Example 1) ○ Apparatus 5I was placed in a 14sus autoclave equipped with an induction stirrer.
zC1* Connect the charging pump and 5izC1! s
can be charged into the autoclave using a dip tube.

A dip pipe for charging inert gas is also installed.

The discharge pipe for the produced monosilane and disilane should be kept at -10°C.
Connect the cooled trap to the
Connect a disilane collection trap cooled to 30°C.

After that, a monosilane collection trap cooled with liquid nitrogen is installed.

The entire system is made into a helium atmosphere with a gauge pressure of 0.2 Ky'cr/l.

08I2CI! The n-butyl ether used as the reduction reaction solvent in No. 6 was dehydrated, and gas replacement was performed by blowing helium into the solution.

LiAl! Ha 41.8 t (0.11 mol) 2
It was suspended and dissolved in 80rrLe of n-butyl ether and charged into an autoclave.

The autoclave was heated to 35°C and stirred.

8rzC1@26.9 f (0.1 mol) to 12-O
d in n-butyl ether and charged over 2 hours using a metering pump.

As the reaction progresses, a small amount of disilane, a by-product monosilane, and a gas mainly composed of hydrogen are released, but everything other than hydrogen is collected by a trap.

After charging 8rxC1*, the mixture was stirred for 1 hour to allow complete reaction.

Thereafter, the temperature of the autoclave was raised to 60° C., and helium was blown into the autoclave at a rate of 0.247 ml for 3 hours.

Disilane entrained in helium is collected in a cold trap.

The yield of disilane was 501, and the yield was 80%.

The impurity 5iHs-CHz-8rHs was hardly detected even by gas chromatography analysis.

Note that even after helium injection was continued for 24 hours, no further disilane was collected.

Comparative Example 1 A reduction reaction was carried out using the same apparatus as in Example 1, but the temperature of the autoclave was not raised to 60°C after the reduction reaction, and the disilane collected in the cooling trap was not blown in. The percentage was 24%.

Comparative Example 2 A reduction reaction was carried out using the same equipment and method as in Example 1, but then the autoclave was heated to 110°C, which is close to the boiling point of n-butyl ether, and helium was blown in as in Example 1. . The yield of disilane was 77%, and 4 wt % of 5iHa-CHz-8iH3, an impurity, was mixed in.

Note that this gas mixed with 5iHs -CH2-8iHa is passed from the palm through an activated carbon layer to form 5iHs -C
Although an attempt was made to remove H2-8iHi, the concentration remained unchanged before and after the activated carbon layer, and purification could not be achieved.

Examples 2 to 6, Comparative Example 3.4 Reduction was performed using the same equipment and method as in Example 1.

Then, we conducted a study by changing the temperature inside the autoclave when helium was blown into the autoclave.

The experimental conditions and results are summarized in a table.

The temperature inside the autoclave when injecting sihelium is 10℃.
It is clear that temperatures between 80°C and 80°C are preferred.

*1 This is the total of disilane that was immediately collected in the trap during the reduction reaction and disilane that was trapped along with helium.

*2 Disilane is displayed as Zoo.

Example 6 The same equipment as in Example 1 was used.

Liquid paraffin was used as a solvent, dehydrated, and helium was blown in to perform gas replacement.

73.8 t of a mixture of 7Qwt% diethylaluminium hydride and 30wt% triethylaluminum was dissolved in 200 m43 of liquid paraffin. In this case, there are 06 moles of diethyl aluminum hydride and 0.194 moles of triethyl aluminum? 17'c.

Add ethylaluminum dichloride 24,6 to this mixture.
f (0,j94-T-ru) for 50m! was dissolved in liquid paraffin and added dropwise.

This mixture of three types of alkyl aluminum compounds was placed in a container and degassed at 30° C. under a reduced pressure of 211IIIg for 20 minutes.

Thereafter, the mixture was placed in a helium atmosphere and placed in an autoclave.

The autoclave was heated to 40°C and stirred.

5isCt! s 26.9 f (0.1 mol) was dissolved in 100 mJ3 of liquid paraffin and charged over 2 hours using a metering pump. After the charging was completed, the mixture was stirred for 1 hour.

Thereafter, the temperature of the autoclave was raised to 60° C., and helium was blown into the autoclave at a rate of 0.2 n/min for 3 hours.

The yield of disilane was 77%.

The impurity 5iHs-CH*28iHs was not detected by gas chromatography analysis and was

Claims (1)

[Claims] In a method for obtaining disilane by reducing a disilane 6 derivative in a solvent, the reaction is carried out at normal pressure or under pressure, and 10 to 8
A method characterized in that sidisilane is obtained by separating it from a solvent by blowing an inert gas into a reaction solution heated to 0°C.