JPH0436090B2 - - Google Patents

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a method for producing monosilane.

[Prior art]

With the rapid growth of the electronics industry market, demand for monosilane has increased rapidly in recent years as a raw material gas for forming semiconductor thin films in ICs, solar cells, photoreceptor drums, etc. A common method for producing monosilane gas is to reduce chlorosilanes such as silicon tetrachloride or silicon trichloride with an alkali metal hydride or an alkyl aluminum hydride. Monosilane as a raw material gas used in the electronics field described above is required to have extremely high purity. To this end, attempts are being made to meet this demand by increasing the amount of adsorbent used during adsorption purification treatment and by removing inert gas along with the monosilane product.

[Purpose of the invention]

For example, when monosilane gas is used as a raw material and subjected to glow discharge decomposition or CVD treatment to form a semiconducting silicon thin film to form an amorphous silicon solar cell, we believe that small amounts of impurities, especially nitrogen, may affect battery performance. It has been found that there is a deep correlation, and that by reducing this amount to an extremely small amount, the deterioration characteristics over time can be significantly improved. However, with the conventional methods as described above, it is extremely difficult to effectively purify monosilane to a level where the nitrogen and oxygen contents are 1 ppm or less, or 0.5 ppm or less.

The object of the invention is therefore to reduce the nitrogen content, e.g.
An object of the present invention is to provide a method for producing ultra-high purity monosilane with an oxygen content of 1 ppm or less and an oxygen content of 0.5 ppm or less.

[Disclosure of the invention]

The above object of the present invention is to reduce one or more chlorosilanes represented by the general formula SiN _o Cl _4-o (where n represents 0, 1, 2 or 3) to produce monosilane. In the method for producing chlorosilanes and/or substantially nitrogen- and oxygen-free
Alternatively, this can be achieved by using a reducing agent, and in some cases a solvent, as a reaction raw material.

The present invention will be explained in detail below.

The chlorosilanes represented by the general formula SiH _o Cl _4-o are silicon tetrachloride, trichlorosilane, dichlorosilane, and monochlorosilane. Monosilane is produced by reducing one or more of these chlorosilanes by a known method using a reducing agent. As the reducing agent, metal hydrides such as alkyl aluminum hydride, lithium hydride, and lithium aluminum hydride are used. When a metal hydride is used as the reducing agent, dibutyl ether, tetrahydrofuran, etc. are used as the solvent.

In the present invention, chlorosilanes, reducing agents, and optionally solvents (hereinafter referred to as reaction system raw materials)
is used in a state substantially free of nitrogen and oxygen. Here, the state of substantially not containing nitrogen or the like means that the nitrogen and oxygen contents are below the detection limit of gas chromatography. In other words, nitrogen is
The content of oxygen may be less than 1 ppm, and the content of oxygen may be less than 0.5 ppm.

Nitrogen and oxygen can be substantially removed from these reaction raw materials by degassing under reduced pressure or by purging (stripping; dispersion treatment) with hydrogen. A liquid or solid reaction material having a high boiling point is preferably degassed under reduced pressure. Furthermore, purging with hydrogen is effective for liquids with low boiling points. For example, chlorosilanes such as silicon tetrachloride and trichlorosilane are purged with hydrogen,
Drives out dissolved oxygen and nitrogen. At the same time, argon and the like contained can also be removed from the raw material.
When an alkyl aluminum hydride is used as the reducing agent, it is preferable to purge with hydrogen, but when an alkyl aluminum hydride with a high boiling point is used, degassing under reduced pressure can also be performed. Further, when a metal hydride such as lithium hydride or lithium aluminum hydride is used as a reducing agent, a solvent such as dibru ether or tetrahydrofuran is usually used, and in this case, it is preferable to purge the solvent with hydrogen. The conditions for purging with hydrogen are appropriately selected depending on the properties and quantities of the substance to be treated.

For example, aluminum diethyl hydride
Nitrogen and oxygen are substantially removed by bubbling 500 with hydrogen at 50/hour for 4 hours at 35°C. In addition, nitrogen and oxygen are substantially removed from silicon tetrachloride 100 by bubbling hydrogen at 10/hour for 4 hours at room temperature.

As described above, a solution containing chlorosilanes, a reducing agent, or a reducing agent from which nitrogen and oxygen have been substantially completely removed is supplied to the reactor, and the pressure is 0 Kg/cm ² G~10
Monosilane is produced by performing a reduction reaction at Kg/cm ² G and a temperature of 10°C to 150°C. Monosilane dissolved in the reaction solution is sent to a purification process together with monosilane gas generated by stripping with hydrogen. Purification is carried out using adsorbents such as activated carbon and molecular sieves. The purified monosilane gas is condensed in a condenser, and then hydrogen gas is separated in a gas-liquid separator and stored in a product storage tank.

〔Example〕

The present invention will be specifically explained below using examples.

Example 1 A 1 m ³ autoclave was charged with 500% aluminum diethyl hydride and bubbled with hydrogen at 50% per hour at 35°C for 4 hours. Next, 100 g of silicon tetrachloride, which had been bubbled with hydrogen at room temperature for 4 hours at a rate of 10 g/h, was supplied to the autoclave at a rate of 20 g/h. The pressure became 9Kg/cm ² G. Next, while supplying 10 Nm ³ of hydrogen per hour to the autoclave, the produced monosilane was stripped and purified through an adsorption tower packed with 10 activated carbons and then an adsorption tower packed with 5 molecular sieves. Monosilane was obtained. The nitrogen content in this monosilane was 1 ppm or less, and the oxygen content was 0.5 ppm or less.

Comparative Example 1 15 kg of monosilane was obtained in the same manner as in Example 1 except that aluminum diethyl hydride and silicon tetrachloride were not bubbled with hydrogen. Nitrogen and oxygen in the monosilane were 5 ppm and 2 ppm, respectively.

[Effects and industrial applicability of the invention]

According to the present invention, nitrogen can be reduced to 1 ppm or less by simply performing an extremely simple operation such as purging the raw materials of the reaction system.
It is now possible to produce ultra-high purity monosilane containing less than 0.5 ppm of oxygen, and when used in, for example, amorphous silicon solar cells, this monosilane can significantly improve the performance of the battery, especially its aging characteristics. can.

On the other hand, monosilane produced without the treatment of the present invention normally contains about 5 ppm of nitrogen and 2 ppm of oxygen;
It is extremely difficult to achieve ultra-high purity of oxygen below 0.5 ppm.

Claims (1)

[Claims] 1 General formula, SiH _o Cl _4-o (where n is 0, 1,
Represents 2 or 3. ) In the method of producing monosilane by reducing one or more chlorosilanes, nitrogen is reduced to less than 1 ppm and oxygen is reduced to less than 0.5 ppm by degassing under reduced pressure or purging with hydrogen. A method for producing high purity monosilane, characterized by using chlorosilanes and a reducing agent.