JPS61275125A - Stabilizing method for hexachlorodisilane - Google Patents

Abstract

PURPOSE:To stabilize the hexachlorodisilane by contacting further the hexachlorodisilane purified by distillation, with a zeolite or a silica gel, thereby removing a substance promoting the decomposition of the hexachlorodisilane. CONSTITUTION:The purity is improved by purifying the hexachlorodisilane by distillation thereof. And then, the purified hexachlorodisilane is brought into contact with the zeolite or the silica gel at a temp. of 5-100 deg.C, for 1min-50hr, thereby the substance promoting the decomposition is removed and the hexachlorodisilane with is easy to decompose is stabilized.

Description

[Detailed Description of the Invention] [Technical Field] The present invention purifies easily decomposed hexachlorodisilane,
Concerning methods of stabilization.

[Background technology]

In recent years, with the development of the electronics industry, the demand for silicon for semiconductors such as polycrystalline silicon or amorphous silicon has increased rapidly.

Polychlorosilane 5inCt2n represented by formula (1)
+2 (n>2) (1) has recently become particularly important as a raw material for semiconductor device manufacturing.

Of course, these can be thermally decomposed as they are to produce amorphous silicon, etc. (Belgium Patent Specification No. 889)
523), further reduced to a polysilane represented by formula (2), 5inHzn+g (n>2) (2)
It is common to thermally decompose this to produce silicon for semiconductors.

However, polysilanes, especially disilane (Si2Hs),
When an amorphous silicon film is formed by thermal decomposition or glow discharge decomposition, there are advantages such as the deposition rate of the film formed on the substrate is much higher than that of monosilane (SiH4), and the film has excellent electrical properties. Demand is expected to increase significantly in the future as a raw material for solar cells or photoreceptor drums (Japanese Patent Laid-Open No. 5.5-83929).

The method for producing hexachlorodisilane itself is well known and typically involves chlorinating particles of a metal-silicon alloy such as calcium silicon, magnesium silicon, or ferrosilicon at high temperatures, or by chlorinating the silicon particles themselves at high temperatures. (U.S. Pat. No. 2,602,72, U.S. Pat.
-65730).

The product of the above reaction is a synthetic liquid (chlorinated synthetic liquid) that is liquid at room temperature and contains various polychlorosilanes corresponding to n=1.2.3, . The content ratio of various polychlorosilanes in the synthesis solution varies depending on the reaction conditions such as the reaction temperature, the concentration of chlorine gas introduced, and the residence time, but usually tetrachlorosilane, hexachlorodisilane, and octachlorotrisilane are used. It is the king of Silane and makes up the majority of its composition. Hexachlorodisilane can be obtained by separating the above-mentioned chlorinated synthetic solution by distillation under normal pressure or reduced pressure. However, by distillation purification, it was not possible to obtain stable hexachlorodisilane, although the purity was high. That is, when hexachlorodisilane purified by distillation is left to stand, decomposition proceeds gradually even at room temperature, and it is not possible to prevent the production of decomposed products such as silicon tetrachloride and chlorine.

However, when disilane is synthesized by reducing hexachlorodisilane containing such decomposition products, the decomposition products are also reduced at the same time. For this reason, impurities such as monosilane are mixed into disilane, resulting in problems such as a decrease in the purity of disilane and a decrease in yield.

Therefore, in order to obtain disilane of high purity at all times, it has been desired to develop a method for stabilizing hexachlorodisilane by removing substances that cause decomposition of hexachlorodisilane in addition to distillation.

[Disclosure of the invention]

Recently, the present inventors have conducted intensive studies on a method for stabilizing hexachlorodisilane, which is easily decomposed, and found that by further contacting distilled and purified hexachlorodisilane with zeolite or silica gel and purifying it, it can be left at room temperature. The inventors have discovered that it is possible to obtain stabilized, highly pure hexachlorodisilane that does not decompose even when exposed to heat, and has thus arrived at the present invention.

Zeolite as used in the present invention refers to a silicate having ion exchange properties, and may be a natural product or a synthetic product.

When using this zeolite, it is preferable to heat it in advance to remove adsorbed water and the like. There is no particular restriction on the size, and depending on the device used for contact, anything from powder to pellet shape can be used. Furthermore, silica gel refers to an amorphous silicic acid polymer, and any type of silica gel can be used as long as it is derived from a water glass-acid aqueous solution. is preferred. Before using this silica gel, it is preferable to heat it in advance to remove adsorbed moisture and the like. Furthermore, there is no particular restriction on the size of the silica gel, and any size can be used depending on the form of the device used for contact.

There is no particular restriction on the type of device used for contacting, and any of the following types can be used: stirred tank type, fixed bed type, moving bed type, and fluidized bed type. Generally, it is preferable to fill a fixed bed type container with zeolite or silica gel and continuously pass the hexachlorodisilane to be treated from above.

There is no particular restriction on the temperature at which hexachlorodisilane is brought into contact with zeolite or silica gel;
℃ range, but a temperature around room temperature is preferred from the viewpoint of operability. The contact time also varies depending on the type of device used, but is usually in the range of 1 minute to 50 hours.

The present invention will be explained below with reference to Examples.

Example 1 Hexachlorodisilane with a purity of 98% obtained by the method of Example 1 of Japanese Patent Application No. 58-65730 was further distilled under reduced pressure to obtain hexachlorodisilane with a purity of 99.9%.

Next, the inside diameter is 2 in a dry box filled with nitrogen.
0IE111 Pelletized molecular sieve 5 with a diameter of 1/16 inch baked at 400°C for 5 hours in a glass tube with a length of 20c1n and a sintered glass filter on the bottom.
Filled with 50 g of A, then filled with 999% pure hexachlorodisilane. Thereafter, hexachlorodisilane purified by distillation at room temperature was supplied from the top over a period of 50-7 hours, and extracted from the bottom at the same rate of <50 d/hour.

The purity of the extracted liquid was the same as that of the supplied liquid (999%). When this treated liquid was left at about 15° C. for one month and analyzed again, the purity was 999% and there was no change in purity.

Comparative Example 1 The hexachlorodisilane used in the treatment of Example 1 was left untreated for - months in the same manner as in Example 1. When the purity was analyzed after - months, the purity had decreased to 98.7%, and silicon tetrachloride and other substances were found to have been produced.

Example 2 Purification was carried out in the same manner as in Example 1, except that 10 to 42 mesh silica gel calcined at 200° C. for 4 hours was used instead of Molecular Sieve 5A.

The purity of hexachlorodisilane immediately after treatment was 999%. Similarly to Example 1, the purity after standing for one month was 998%, indicating that hexachlorodisilane was sufficiently stabilized in this case as well.

Claims (2)

[Claims] (1) A method for stabilizing hexachlorodisilane, which is characterized by bringing hexachlorodisilane into contact with zeolite or silica gel. (2) The method according to claim 1, wherein the hexachlorodisilane is purified by distillation.