JPH0375202A - Purification of gas of hydrogenated substance - Google Patents

Abstract

PURPOSE:To efficiently adsorb or remove moisture content without generating adsorption of a hydride gas and efficiently obtain a purified hydride gas of desired concentration by bringing a crude hydride gas into contact with an adsorbing agent comprising a molded article containing zinc oxide as a principal ingredient. CONSTITUTION:An aqueous solution of soda ash is added to an aqueous solution of zinc nitrate or zinc chloride, etc., and basic zinc carbonate is precipitated, then the precipitate is filtered, washed with water and zinc oxide is produced by means of drying and burning, etc. Next, an adsorbent composed of a molded article containing zinc oxide as a principal ingredient is produced by means of mixing a lubricant into the powder of zinc oxide and molding, etc. Then, said adsorbent is brought into contact with a crude hydride gas and moisture contained in the crude hydride gas is removed to afford a purified hydride gas. Besides, an adsorbent containing zinc oxide as a principal ingredient does not adsorb a hydride gas differing from a normal synthetic zeolite.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for purifying hydride gas, and more specifically, to a method for purifying hydride gas, and more specifically, to a method for purifying hydride gas, and more specifically, to purifying a hydride gas that can remove moisture contained as an impurity in hydride gas to an extremely low concentration. Relating to a gas purification method.

Hydride gases such as arsine, phosphine, silane, and diborane are important raw materials and ion implantation gases for manufacturing compound semiconductors such as gallium-arsenic (GaAs) and gallium-phosphorus (GaP). The amount used is increasing year by year, and at the same time, as semiconductors become more highly integrated, there is a demand for materials with extremely low impurity content.

[Conventional technology]

Hydride gases used in semiconductor manufacturing are generally commercially available in diluted form with hydrogen gas or inert gas, in addition to pure hydride gas.

These hydride gases contain impurities such as oxygen and moisture.

To remove water, we usually use synthetic zeolites that are easy to handle, such as Molecular Sieve 4A and 5A (Union Carbide, USA), or high-silica zeolite T S Z -600) 10E (manufactured by Tosoh). It is possible to adsorb and remove the dew point down to -80'C1 or even lower by using a wetting agent.

[Problem to be solved by the invention]

However, these moisture adsorbents generally also adsorb hydride gases such as arsine and phosphinone at the same time. There is a problem that it takes a considerable amount of time, and the lower the hydride gas concentration in the raw material gas, the longer it takes.

Furthermore, adsorbents that have adsorbed a large amount of hydride gas pose safety problems when handling them when they are replaced.

[Means to solve the problem]

The inventors of the present invention have conducted intensive research to efficiently remove water contained in hydride gas to an extremely low concentration and to reach a specified concentration in a short time after starting refining. The present invention was completed by discovering that by using a molded body as a component, water is adsorbed but hydride gas is not adsorbed.

That is, the present invention provides a hydride gas characterized in that water contained in the crude hydride gas is removed by bringing the crude hydride gas into contact with an adsorbent made of a molded body containing zinc oxide as a main component. This is a purification method.

The present invention can be applied to hydride gas alone, hydride gas diluted with hydrogen (hydrogen gas space) and inert gas (inert gas space) such as nitrogen or argon (hereinafter collectively referred to as crude hydride gas). Applicable for removing contained moisture.

The hydride gas includes arsine, phosphine, silane, diborane, etc., and is a hydride gas mainly used in semiconductor manufacturing processes.

The adsorbent used in the present invention is a molded body containing zinc oxide as a main component.

For zinc oxide, there is a wet method using an aqueous solution of zinc salt as a raw material,
Products manufactured by various methods such as the French method using metallic zinc as the raw material and the American method using zinc ore as the raw material can be used, but the wet method is preferable because it produces particles with small particle size and a large specific surface area. Generally preferred. As a wet method, for example, a soda ash aqueous solution is added to an aqueous solution of zinc nitrate, zinc chloride, etc. to precipitate basic zinc carbonate, which is filtered, washed with water, dried, and further heated at 200 to 700'C.
Zinc oxide is produced by firing the zinc oxide. In addition, an appropriate adsorbent may be selected from commercially available zinc oxide.The adsorbent used in the present invention may be formed by molding zinc oxide into pellets or the like, or by crushing the molded material into appropriate sizes. It is used as As a molding method, a dry method or a wet method can be used. For example, the former method involves mixing zinc oxide powder with a small amount of lubricant such as graphite or talc and molding it into tablets, while the latter method involves adding a binder such as alumina cement and water to zinc oxide and kneading it. There is a method of extrusion molding. These are refired if necessary.

The mixing ratio of alumina cement to zinc oxide is usually 50 g or less per 100 g of zinc oxide, preferably 10 g.
~30g. Alternatively, a molded body of zinc oxide may be obtained, for example, by adding a lubricant, a binder, etc. to the basic zinc carbonate stage and then molding the product and firing it at 300 to 700°C.

- For the inside of the shell, a wet method is preferable due to ease of processing.

There are no particular restrictions on the size and shape of the molded body, but representative examples include spherical, cylindrical, and cylindrical shapes, and in some cases, these are crushed into appropriate sizes before use. The size of the molded body is 1 to 10 mm in diameter if it is spherical;
If it is cylindrical, it has a diameter of 1 to 10 mm and a height of about 2 to 20 mm, and if it is an irregular shape, it has a sieve opening of 0.84 to 5.66 mm.

The density of the molded product used in the present invention is usually 0.6 to 3.5 g.
/d, preferably in the range of 0.8 to 2.5 g/-.

In the present invention, density refers to the weight of a molded body (grain) divided by the geometric volume of the molded body.

In addition, the packing density when the molded body is packed into an adsorption tube is usually 0.5 to 2.0 g/ml! Preferably 0.6 to 1.5
g/-.

In the present invention, the adsorbent is usually packed in a purification column, and by introducing a crude hydride gas containing moisture into the adsorbent and bringing them into contact, the moisture in the gas is adsorbed and removed, resulting in a purified gas with a low dew point.

Although the lower the adsorption temperature, the lower the adsorption temperature is generally preferred, it is sufficient as long as it is about 80°C or less, and usually has sufficient adsorption performance at room temperature of 60°C or less, and does not particularly require cooling.

In practice, the packing length of the adsorbent packed into the refining column is usually 5
It is 0 to 1500 mm. If the filling length is shorter than 50 mm, the water removal rate may decrease, and if it is longer than 1500 am, pressure loss may increase.

The velocity of the crude hydride gas during contact is about the same as when using synthetic zeolite, and the cylinder linear velocity is usually 150 cm.
/sec or less, preferably 1 to 70 Cm/sec. In addition, there is no particular limit to the pressure at the time of contact, but in practice 1
It is often carried out in the range of ~10Kg/cm2G.

In the present invention, in the water removal step using the above-mentioned adsorbent,
If desired, it is also possible to combine a deoxidizing step using a metal-based deoxidizing catalyst or the like, whereby oxygen is removed at the same time as moisture, and a purified hydride gas of extremely high purity can be obtained.

〔Effect of the invention〕

Since the present invention uses a molded body mainly composed of zinc oxide as an adsorbent, hydride gas is not adsorbed unlike ordinary synthetic zeolite, and purified hydride gas can reach a predetermined concentration in a short time. can be reached and moisture can be removed efficiently.

〔Example〕

Examples 1 to 4 While stirring a 20 wt % aqueous solution of zinc nitrate in a stirring tank, a 20 wt. This precipitate was filtered, washed, dried at 120°C for 10 hours, and then
Zinc oxide was obtained by firing at 00°C for 5 hours. A small amount of water was added to a mixture of 41 g of zinc oxide obtained in this way and 9 g of alumina cement, and the mixture was kneaded in a kneader.
The extrusion molded product was dried at 120° C. for 2 hours. The density of this material was L9g/mI2.

This molded product was crushed into 20-35 mesh 3
24- with an inner diameter of 37.1 mm and a length of 400 mm
Packed into a refining cylinder made of S 316 (packing density 1.3g/
d') I did.

Dry nitrogen gas is supplied to the purification cylinder at normal pressure at 350℃ and flow rate 1940℃.
-/min (LV = 3cm/sec)
After the activation treatment was carried out by flowing the mixture for 3 hours, the mixture was cooled to normal pressure.

This purification cylinder contains 10vol containing water as an impurity.
% concentration of crude hydride gas (hydrogen base)
When the concentration of hydride gas in the purified gas at the outlet was measured by flowing at did.

At the same time, the dew point of the outlet gas was measured using a capacitance dew point meter and was found to be -90°C or lower, and although purification was continued in this state for 100 minutes, the dew point remained at 90°C or lower. Furthermore, the gas flow rate is set to 194 (hyd!/ mix < LV =
3 cm), but no change was observed in the dew point. The results are shown in Table 1.

Example 5.6 Crude silane gas (hydrogen base) containing water as an impurity at a concentration of 1100 pp was added at 970 ytl/mm (
LV:=1.5 cm/sec) and 6480d
/min (LV=10 cm/sec) and the time required for the silane in the outlet purified gas to reach its original concentration was measured, and the time was 28 m1n (Example 5) and 4 m1n, respectively.

Further, the dew point of the purified gas at the outlet was below -90°C, and even after 100 minutes, it remained below -90°C even though the purification was continued. The results are shown in Table 1.

Table 1 Comparative Examples 1 to 4 Molecular sieve 5A (Union Showa ■ 1/16 pellet product) 324 m12 was filled in the same purification column as in the example at 300 mm (filling density 0.75 g/m), and dry nitrogen gas was added. After performing activation treatment by flowing at 350°C for 3 hours, it was cooled to room temperature.

970 mQ//
min (LV = 1.5 cm/see
) so that the hydride gas in the outlet gas becomes the original 10vo
When the time taken to reach 1% was measured, it took 1 to 3 hours. The results are shown in Table 2.

Comparative Examples 5 to 6 Nine volumes of crude silane at the same concentration of 1100 pp as used in Example 5.6 were added to the two refining cylinders prepared in Comparative Examples 1 to 4, respectively.
70m12/min (L V = 1.5 ct
x/sec) and 6480m/min (L
The time taken for the silane concentration in the outlet purified gas to reach the original 1100 pp by flowing at V = 10 cm/sec) was 600 mi+ (Comparative Example 5) and 180 m1n (Comparative Example 6).Results are shown in Table 2.

Table 2

Claims (1)

[Claims] A method for purifying hydride gas, which comprises bringing crude hydride gas into contact with an adsorbent made of a molded body containing zinc oxide as a main component to remove moisture contained in the crude hydride gas.