JPH06102133B2 - Method for removing arsine and phosphine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to arsine (AsH ₃ ) which is known as a gas having the highest toxicity among special material gases used in semiconductor manufacturing plants and the like, and It relates to a method for removing phosphine (PH ₃ ).

[Conventional technology]

AsH ₃ and PH ₃ have been conventionally used as a material gas for semiconductors, and the amount thereof used has been increasing year by year as the production amount and diversification of semiconductor elements have increased.

AsH ₃ gas and PH ₃ gas are extremely toxic among special material gases, and it is known that even a very small amount is harmful to the human body, and some methods of removing harm have been proposed. However, most of them use solid adsorbents, and solid-phase adsorption methods involving chemical reactions have been widely used.

In addition, among the conventional detoxification methods, there are methods that use a wet absorption method and use an alkaline liquid such as NaOH or an oxidizing agent.

[Problems to be solved by the invention]

A high removal rate can be expected for the removal by the adsorption method, but there are aspects inadequate in cost and other points for large-scale processing. On the other hand, although the wet absorption method is originally suitable for processing a large amount of gas, it has a problem in terms of life and removal rate of the absorbing liquid.

In view of the present situation, the present invention can handle a small amount to a large amount of processing gas, can process a low concentration gas to a high concentration gas, and has a long life of the absorbent. It is an object of the present invention to provide a method for removing arsine and phosphine, which is significantly improved.

[Means for solving problems]

According to the present invention, this object is characterized in that a silver nitrate solution is used as an absorbent, and the silver produced in the treatment reaction is oxidized by hydrogen peroxide, oxygen, ozone, air, etc. and then dissolved in an aqueous nitric acid solution. It is achieved by providing a method for removing arsine and / or phosphine in a gas produced by a wet absorption method.

A schematic diagram of an apparatus for carrying out the present invention is shown in FIGS. 1 and 2.

In FIG. 1, the gas discharged from the gas supply box 1 for quantitatively supplying AsH ₃ gas and / or PH ₃ gas is guided to the absorption tower 3 through the conduit 2. The absorption tower 3 is filled with a filler, and the gas passing through the absorption tower 3 is guided to the adsorption tower 5 by the conduit 4. The adsorption tower 5 uses AsH ₃ gas and / or
Or, when PH ₃ gas is not removed by the absorption tower 3 and is installed for emergency, it is not a necessary condition for carrying out the present invention. The gas exiting the adsorption tower 5 passes through the conduit 6 and is exhausted by the exhaust blower 7. The absorbing liquid is stored in the tank 8, is pumped to the conduit 11 by the circulation pump 9, and is sprayed from the upper part of the absorption tower 3 onto the packed bed. AsH ₃ gas and / or PH ₃ gas is contacted with the absorption liquid in the packed bed, liquid played the absorption of AsH ₃ and / or PH ₃ in the gas is a conduit 1
Pass 0 and return to tank 8.

On the other hand, Ag deposited by the absorption reaction stored in the tank 8
The absorption liquid containing is pumped into the conduit 15 by the pump 14 and is sprayed to the upper part of the oxidation tower 13. The oxidation tower 13 is filled with activated alumina or activated carbon as a filler. The gas supplied by the oxidizing gas supply box 12 is sent to the oxidation tower 13, where it reacts with the absorbing liquid and Ag, and joins with the above gas in the conduit 2,
The oxidized Ag and the absorbing solution are returned to the tank 8.

In addition, S1 is a gas concentration detection port before absorption, and S2 is a gas detection port after absorption. Use an absorbent that has a silver nitrate concentration of 10% by weight or less and is acidified by adding nitric acid.

FIG. 2 omits the oxidation process of Ag by the oxidizing gas in FIG. 1, and hydrogen peroxide is added to the absorbing liquid stored in the tank 8 instead of using the oxidizing gas. The removal process of AsH ₃ gas and / or PH ₃ gas is the same as in FIG.

[Action]

The gas introduced into the absorption tower 3 through the conduit 2 comes into contact with the absorption liquid scattered on the packed bed from the upper part of the absorption tower 3 in the packed bed, and AsH ₃ gas and / or PH ₃ gas in the gas phase Are absorbed in the liquid phase.

The removal reaction of AsH ₃ and PH ₃ by the silver nitrate solution is expressed by the following equation.

AsH ₃ ＋ 6AgNO ₃ → 6Ag ＋ H ₃ AsO ₃ ＋ 6HNO ₃ PH ₃ ＋ 6AgNO ₃ → 6Ag ＋ H ₃ PO ₃ ＋ 6HNO ₃ On the other hand, the following reaction occurs in the oxidation tower 13 or when hydrogen peroxide is added.

2Ag + 1 / 2O ₂ → Ag ₂ O Ag ₂ O + 2NHO ₃ → 2AgNO ₃ + H ₂ O [Example 1] The results of carrying out the present invention in the apparatus shown in FIG. , As shown in Table 1. The absorption tower 3 has a cylindrical shape with an inner diameter of 100 mm and is used as a packing material.
This is a wet packed tower with facing contact in which a 5 mmφ lashing ring is packed in 600 mm. The absorption liquids were AgNO ₃ 5% and HNO ₃ 1.5N.

The gas before absorption treatment was measured in S1 and the gas after absorption treatment was measured in S2.

In each case, precipitation of Ag was confirmed at the start of the experiment, and a considerable amount of Ag fine powder was precipitated at the end of the experiment.

Example 2 In the apparatus shown in the schematic diagram of FIG. 1, the precipitated Ag-containing absorbing liquid was brought into contact with an oxidizing gas, and the Ag concentration and As in the absorbing liquid when using a filler together The concentration was measured and the recycling of Ag was confirmed.

Before treatment, the AsH ₃ and PH ₃ gas concentrations were kept constant at 100 ppm, the absorption liquid was AgNO ₃ 5% (Ag 6,400 μg / ml) 15, the oxidative gas flow rate was about 5 / min, and the required treatment gas amount was absorbed. It was carried out at a gas flow rate of 20 cm / sec (94 / min) in the tower 3.

Precipitation of Ag was confirmed at the same time as the start of the experiment, but almost all Ag was dissolved at the end of the experiment, and no fine Ag powder was confirmed.
In addition, about 20ppm of NOx was detected in the exhaust gas.

[Example 3] In the same apparatus as in Example 2, a sub-treatment gas having an AsH ₃ gas concentration of 50 ppm was 94 / min, and an absorbing solution was AgNO ₃ 0.1% (640 μg as Ag).
(g / ml) 15 and the results obtained by aerating the oxidation tower 13 filled with activated carbon with air are as follows.

Treatment time 90 minutes AsH ₃ concentration after treatment <0.05ppm Ag in absorption liquid 635 μg / ml (9.5 g / 15) As in absorption liquid 94 μg / ml (1.41 g / 15) [Example 4] Outline shown in Fig. 2 The results of carrying out the present invention with the apparatus shown in the figure are as shown in Table 3. Absorption tower 3 has an inner diameter of 100 mm
It has a cylindrical shape, and a lashing ring of 15 mmφ is 600 m as a filler.
It is a wet packed tower of m contact packed with facing contact. As the absorbing solution, AgNO ₃ 5%, HNO ₃ 1.5N solution 15 and H ₂ O ₂ 0.3% (wt / V) were added.

The gas before absorption treatment was measured in S1 and the gas after absorption treatment was measured in S2.

Precipitation of Ag was confirmed at the same time as the start of the experiment, but the Ag fine powder that had precipitated about 30 minutes after the start of the experiment disappeared. Also, NOx in the exhaust
Was not detected.

[Embodiment 5] AsH ₃ with a gas concentration of 50 ppm was added in the same apparatus as in Embodiment 4
/ min, absorption liquid is AgNO ₃ 0.1% (640 μg / ml as Ag) 15
The results obtained by adding 0.3% (wt / V) of H ₂ O ₂ to the following are as follows.

Treatment time 90 minutes AsH ₃ concentration after treatment <0.05ppm Ag in absorption liquid 630 μg / ml (9.45g / 15) As in absorption liquid 94 μg / ml (1.41g / 15) [Effect] The method of absorbing silver nitrate solution is Although it has been reported at the laboratory level from the past, it is not the case that it has been used on the industrial practical scale. In the present invention, as a result of conducting a practical scale experiment using a silver nitrate solution, as shown in Example 1, it was confirmed that the removal performance was extremely excellent.

However, due to the absorption reaction of the silver nitrate solution, Ag precipitates as fine powder, which shortens the life of the absorbing solution, resulting in a high running cost method. Precipitated Ag
Is dissolved by increasing the concentration of nitric acid, but it has problems such as odor and corrosion. At a practical nitric acid concentration, the reaction between Ag and nitric acid is very slow, and nitric oxide is generated during the reaction. To do.

On the other hand, in the present invention, Ag is oxidized by supplying an oxidizing gas such as oxygen or air, or by adding hydrogen peroxide, and Ag is converted to nitric acid in a state where nitrogen oxides are not emitted. It was confirmed that the reaction could be carried out promptly.

That is, in Example 3, the Ag is not recycled, is submerged AgTotal weight 9.6g (0.09mol) AgTotal amount and equivalent of As weight 1.13 g (0.015 mol), this with when the AsH ₃ gas amount 0.336 Become,
The AsH ₃ gas amount of Example 3 is less than 0.43. This is because the amount of AsH ₃ gas (0.087
) Has been absorbed.

Also, in Example 5, assuming that Ag is not recycled, the Ag total amount in the liquid is 9.6 g (0.09 mol), the Ag total amount is equivalent to the As amount 1.13 g (0.015 mol), and the actual As amount in the liquid is 1.41 g. It was confirmed that more than the equivalent amount of AsH ₃ gas was absorbed due to Ag recycling, exceeding the theoretical value of 1.13 g.

[Brief description of drawings]

1 and 2 are schematic diagrams of an apparatus used for implementing the present invention.

Continuation of the front page (56) References JP-A-50-151788 (JP, A) JP-B-56-17137 (JP, B2)

Claims (4)

[Claims] 1. Removal of arsine and / or phosphine characterized by absorbing arsine and / or phosphine in a silver nitrate solution, oxidizing silver produced by the absorption reaction, and then dissolving and reusing it in a nitric acid aqueous solution. Method 2. The method according to claim 1, wherein the silver produced by the absorption reaction is dissolved in a nitric acid aqueous solution containing hydrogen peroxide to suppress the generation of NOx and accelerate the oxidative dissolution of silver. Method for removing arsine and / or phosphine 3. The method for removing arsine and / or phosphine according to claim 1, characterized in that silver produced by the absorption reaction is oxidized with an oxidizing gas and rapidly dissolved in nitric acid. 4. The arsine according to claim 1, characterized in that silver produced by the absorption reaction is oxidized in the activated alumina layer or activated carbon layer by being brought into contact with an oxidizing gas to be rapidly dissolved in nitric acid. And / or method for removing phosphine