JPH0443844B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for storing high purity monosilane. More specifically, it relates to a method of storing monosilane in a storage tank that does not contain gases such as oxygen, nitrogen, hydrogen, argon, helium, and methane, which have a lower boiling point than 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. Common methods for producing monosilane gas include reducing chlorosilanes such as silicon tetrachloride or silicon trichloride with an alkali metal hydride or argylaluminium hydride, or reacting an alloy such as Mg ₂ Si with hydrochloric acid or ammonium chloride. It is true.

Monosilane gas obtained by these methods has been purified by adsorption using an adsorbent such as activated carbon or molecular sieve, purified by distillation, or purified by a combination of these methods for practical use. These purification methods are effective against impurities with a boiling point higher than the boiling point of monosilane (-112℃).
Although it has a sufficient purification effect, a sufficient purification effect cannot be obtained for impurities having a boiling point lower than that of monosilane, such as oxygen, nitrogen, hydrogen, argon, helium, and methane. Therefore, it is usually stored in a product tank at a temperature below the boiling point of monosilane with such trace amounts of impurities mixed in, and is then filled into containers such as cylinders and used for various purposes.

[Purpose of the invention]

However, for applications such as semiconductors, solar cells, and photoreceptor drums that require high purity, contamination of low-boiling point substances such as oxygen, nitrogen, hydrogen, argon, helium, and methane in the product monosilane gas is a problem. It has a significant impact on the quality of the product in its application. The present inventors have found that, in particular, for amorphous silicon solar cells, the presence of very small amounts of impurities such as oxygen and nitrogen in the raw material monosilane significantly affects the performance of the cell, especially its aging characteristics. found that it has an effect.

Therefore, an object of the present invention is to provide a method for filling and storing a container with high-purity monosilane gas so that it can be suitably used in fields that require particularly high quality, such as amorphous silicon solar cells. .

[Disclosure of the invention]

The above objects of the invention are achieved by maintaining the monosilane under reflux in a reservoir of liquid monosilane.

The present invention will be explained in detail below.

Monosilanes to which the present invention can be applied include those produced by reducing chlorosilanes using a reducing agent;
Any material manufactured by reacting an alloy such as Mg ₂ Si with hydrochloric acid or ammonium chloride may also be used. Regardless of the manufacturing process, the monosilane entrained with purified hydrogen is condensed and stored in a product holder.

In the present invention, monosilane is maintained in this storage tank under reflux, preferably at around -112°C, which is the boiling point of monosilane. Afterwards,
It is extracted from the storage tank, preferably from the lower part of the storage tank, with a pump, heated with a vaporizer, filled into a container such as a cylinder, and shipped. When extracting monosilane with a pump, monosilane may be extracted in liquid form, but monosilane may also be extracted with a compressor from the gas phase of a storage tank held under reflux and filled into a container.

〔Example〕

The present invention will be specifically explained below using examples.

(Example 1) 3 m ² in a liquid silane holder with 40 jackets
A countercurrent condenser with a heat transfer area of The counterflow condenser was cooled with liquid nitrogen at a pressure of 5 Kg/cm ² G. The holder part was kept cool with 75mm thick urethane foam. Do not pour liquid nitrogen into the jacket of the holder. This holder is supplied with a carrier gas of ^10Nm3 per hour (nitrogen 1500ppm,
Hydrogen containing 100 ppm of oxygen and argon was used to supply 1.2 kg of silane per hour for 10 hours, and 12 kg of liquid silane was stored.

The silane in the holder is kept at boiling point and refluxed in a counterflow condenser.

Liquid silane was extracted from the bottom of the storage tank using a pump, vaporized, and then filled into two 47 cylinders with silane gas. Analysis of impurities in the cylinder revealed 0.7 ppm of nitrogen, the sum of oxygen and argon.
0.3ppm, hydrogen 5ppm, and no methane detected.

(Comparative example 1) Pass liquid nitrogen through the jacket of the holder and -
A cylinder was filled with monosilane in the same manner as in Example 1 except that the temperature was maintained at 120°C. As a result, the impurities in the cylinder were 12 ppm of nitrogen and 4 ppm of oxygen and argon.
It was hot.

[Effects and industrial applicability of the invention]

When monosilane stored by the method of the present invention is filled into a "47 cylinder", for example, the amount of nitrogen mixed in can be 1 ppm or less, the amount of oxygen mixed in can be 0.5 ppm or less, and hydrogen can also be 10 ppm or less, Furthermore, it becomes possible to fill the container with ultra-high purity silicon that does not detect argon, helium, methane, etc. Therefore, monosilane filled into a container in this way can be used for ICs, solar cells,
It is effectively used in applications such as photosensitive drums.

Claims (1)

[Claims] 1. A method for storing high-purity monosilane, which comprises maintaining monosilane under reflux in a liquid monosilane storage tank.