JPH0340901A - Method for refining gaseous hydride - Google Patents

Abstract

PURPOSE:To remove the moisture contained in a gaseous hydride to an extremely low concn. and to appropriately use the hydride as the semiconductor producing raw material by bringing the crude gaseous hydride into contact with an adsorbent consisting of the formed body of a mixture of zinc oxide, aluminum oxide and an alkali compd. CONSTITUTION:Zinc oxide, aluminum oxide, an alkali compd. (e.g. sodium hydroxide) and water are mixed, and the mixture is formed into pellets by extrusion molding, etc., to form the adsorbent. A crude gaseous hydride (e.g. arsine and phosphine) to be used as the raw material for producing the compd. semiconductors of GaAs, GaP,etc., or as the ion implantation gas is brought into contact with the adsorbent to remove the moisture contained in the gas. Consequently, since the adsorbent selectively adsorbs moisture and not a gaseous hydride unlike the ordinary synthetic zeolite, etc., a refined gaseous hydride is efficiently produced in a short time.

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 as base materials and ion implantation gases for manufacturing compound semiconductors such as gallium-arsenic (GaAs) and gallium-phosphorus (GaP). As its usage increases 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 moisture, we usually use dehumidifiers such as synthetic zeolites that are easy to handle, such as Molecular Sieve 4A and 5A (Union Carbide, USA, etc.), or high-silica zeolite T S Z -600HOE (manufactured by Tosoh Corporation). Therefore, it is possible to adsorb and remove dew points up to -80'C1 or even lower.

[Problem to be solved by the invention]

However, these water adsorbents generally adsorb hydrogen gases such as arsine and phosphine (and arsenic gases) at the same time. There is a problem in that it takes a considerable amount of time for the hydride gas in the purified gas discharged from to reach its original concentration, 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 based on the discovery that by using an adsorbent containing aluminum and an alkali compound, water is adsorbed but hydride gas is not adsorbed.

That is, the present invention is characterized in that the moisture contained in the crude hydride gas is removed by bringing the crude hydride gas into contact with a molded body of a composition formed by mixing zinc oxide, aluminum oxide, and an alkali compound. This is a method for purifying hydride gas.

The present invention is applied to hydride gas alone, hydrogen (hydrogen gas space), and hydride gas diluted with an 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 zinc oxide 1. Its main components are aluminum oxide and an alkali compound.

As zinc oxide, an appropriate one may be selected from commercially available products, and precursors such as zinc carbonate, basic zinc carbonate, zinc hydroxide, and organic acid zinc that can be converted to zinc oxide by calcination etc. May be used.

Further, as aluminum oxide, alumina hydrate is usually used, and for example, commercially available alumina sol or highly concentrated alumina made from powdered alumina sol is suitable.

Furthermore, the alkaline compounds include hydroxides, carbonates, bicarbonates, and acetates of alkali metals such as lithium, sodium, and potassium, alkaline earth metals such as magnesium and calcium, and ammonium. Among these, potassium carbonate, potassium bicarbonate, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium hydroxide, ammonium hydroxide, and mixtures thereof are preferred.

The amount of aluminum oxide and alkali compounds relative to zinc oxide is usually 0% aluminum per 1 atom of zinc.
．． 02-0.60 atoms, preferably 0.05-0.40
and the amount of alkali compound is usually from 0.02 to 0.70 atoms, preferably from 0.105 to 0.50 atoms, in terms of alkali metal or ammonium groups.

If the atomic ratio of aluminum is smaller than 0.02, there is a risk that the strength of the molded product will decrease. On the other hand, if it is larger than 0.60, the amount of hydride gas adsorbed will increase, and hydride gas will be There is a possibility that it takes a long time to reach a predetermined concentration. Furthermore, if the atomic ratio of the alkali metal or ammonium group is smaller than 0.02, the strength and adsorption capacity of the molded product will decrease, while if it is larger than 0.70, molding will become difficult.

The adsorbent can be prepared by, for example, adding water to a mixture of zinc oxide or oxide precursor, alumina sol, and an alkali compound and kneading it, or adding water to zinc oxide or its precursor and alumina sol and kneading it. After that, an alkali compound is further added and the resulting cake is formed.

There are various molding methods, such as: ■ extrusion molding the cake of the mixture obtained above and drying the resulting pellet; ■ drying the cake, then crushing it, and adding a lubricant such as graphite to it. There are two methods: 1) forming a mixture into tablets; 2) forming a cake into granules using a granulator.

Among these, it is generally convenient to make a pellet shape by extrusion molding for ease of processing and selection of shape and size. It is preferable to take the form

The molded body becomes an adsorbent by firing at 180 to 600° C., preferably 210 to 450° C., while flowing purified gas.

There are no particular restrictions on the size and shape of the molded body, but representative examples include spherical, cylindrical, and cylindrical shapes. The size is 0.5 to 10 mm in diameter if spherical, 0.5 to 10 mm in diameter and 2 to 20 mm in height if cylindrical.
If the material has an irregular shape such as granules, a sieve with an opening of about 0.84 to 5.66 mm is used.

The density of the molded product used in the present invention is usually 0.5 to 3.0 g.
/m, preferably in the range of 0.7 to 2.5 g/m. In the present invention, density refers to the weight of a molded body (grains) divided by the geometric volume of the molded body.

In addition, the packing density when the molded body is packed in a refining cylinder is usually 0.4 to 2.0 g/- preferably 0.5 to 1.5 g/
It is assumed to be m12.

In the present invention, the adsorbent is usually packed in a purification cylinder, and by passing crude hydride gas containing moisture through 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 cylinder is usually 5
It is 0-1500+nm. When the filling length is shorter than 50 clI11, the water removal rate decreases, and when it is longer than 1500 nm, 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 I 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 composition made of a mixture of zinc oxide, aluminum oxide, and an alkali compound as an adsorbent, hydride gas is not adsorbed unlike ordinary synthetic zeolite, and purified hydrogen The compound gas can reach a predetermined concentration in a short time and can efficiently remove water.

〔Example〕

Examples 1 to 4 Basic zinc carbonate 500g, Cataloid AP (Catalyst Chemical ■
52.4 g (0.16 atom of AI per 1 atom of Zn), 30.0 g of anhydrous potassium carbonate.
2g (KO, 10 atoms per Znl atom) was placed in a small kneader and mixed for 3 minutes, then 280g of water was added and 1
Kneaded for hours. This cake is processed using a small extruder.1.
The pellets obtained by extrusion through a 9φ nozzle plate were rolled into balls using a marmerizer and dried at 110'C for 2 hours. By putting this material in a Matsufuru furnace and firing it at 350℃ for 1 hour, the density was 1.14g/nrl, and the packing density was 0.74.
g/- of adsorbent was obtained.

Crush the molded body to 20-32 mesh and make 324
- was packed into a purification cylinder made of 5US316 with an inner diameter of 37.1 mm and a length of 400 mm (packing density 0.87 g/rnQ).

Dry nitrogen gas in the purification cylinder at normal pressure at 350°C1 flow rate L94
0mQ/mm 8 L V = 3cm/se
After the activation treatment was carried out by flowing for 3 hours in e), the mixture was cooled to room temperature.

This M-made cylinder contains 10vol. water as an impurity.
% concentration of crude hydride gas (hydrogen base) at 970m/
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 found to be ~90°C or lower, and even though purification was continued in this state for 100 minutes, the dew point remained at 90°C or lower. Furthermore, the gas flow rate was set to 1940 mR/min (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 to two purification cylinders prepared in the same manner as in Examples 1 to 4 at a rate of 970 mQ/min.
(L V = 1.5 cm/sec) and 6
When flowing at 480 m1/min (LV=10 cm/sec) and measuring the time it took for the silane in the outlet purified gas to reach its original concentration, 11 peaks were found in each case (Example 5).
And there were two theories.

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

Table 1 Comparative Examples 1 to 4 324 mQ of Molecular Sieve 5A (Union Showa ■ 1/16 pellet product) was packed into the same purification cylinder as in the example for 300 turns (packing density 0.75 g/d), and dry nitrogen gas was added. After performing activation treatment by flowing at 350°C for 3 hours, it was cooled to room temperature.

970all of the same hydrogen-based various crude hydride gases (10vol 1%) used in Examples 1 to 4 were added to this purification column.
/ min (LV = 1.5 cm / sec
) and the hydride gas in the outlet gas is the original 10V.
When the time taken to reach o1% was measured, it took 1 to 3 hours. The results are shown in Table 2.

Comparative Examples 5 to 6 9 pieces of crude silane at the same concentration of 1100 pp as used in Example 5.6 were added to the purified pipes prepared in Comparative Examples 1 to 4, respectively.
70m/min (LV=1.5cm/
sec) and 6480mQ/min (L V
= 10cm/sec) and measured the time it took for the silane concentration in the outlet purified gas to reach the original 1100PP, which was 600 min or more (Comparative Example 5)
and 180 min (Comparative Example 6). The results are shown in Table 2.

Comparative Examples 7 to 9 High silica zeolite (TZS-600HO manufactured by Tosoh Corporation)
E 1.8 pellet product) 324 mQ was placed in the same refining tube as in the example with 307 nΩ (packing density 0.73 g/
mQ) was filled, activated by flowing dry nitrogen gas at 350° C. for 3 hours, and then cooled to room temperature.

This purification cylinder contains 10vol 1% water as an impurity.
of crude phosphine, crude silane and 100 ppm raw silane (all hydrogen based) at 970 d/min each.
The purified gas was passed through a sieve (LV-1, 5 cm/sec), and the time and dew point until the phosphine and silane in the outlet purified gas reached their original concentrations were measured. The results are shown in Table 2.

Table 2

Claims (1)

[Claims] A hydride gas characterized in that moisture contained in the crude hydride gas is removed by bringing the crude hydride gas into contact with a molded body of a composition formed by mixing zinc oxide, aluminum oxide, and an alkali compound. Purification method.