JPH01148331A - Method for making hydride-based waste gas harmless - Google Patents

Abstract

PURPOSE:To properly remove harmful gases such as arsine, phosphine and diborane from hydride-based waste gas contg. the harmful gases besides silane by bringing the waste gas into contact with a treating soln. which is an alcoholic soln. of an oxidizing agent. CONSTITUTION:A treating soln. prepd. by mixing an oxidizing agent such as copper nitrate with an alcohol such as propanol is poured into a reaction vessel 1. Waste gas contg. silane, phosphine, arsine, etc., is blown into the vessel 1 from a line 2 for introducing waste gas to be made harmless. The harmful gases in the waste gas are decomposed and removed by contact with the treating soln. A condenser 15 is fitted to a line 3 for discharging treated gas and the vaporized alcohol in the treated gas is condensed and returned to the vessel 1.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a method for abatement of waste gas containing hydride-based harmful gases such as arsine, phosphine, silane, or diborane. To provide something that can eliminate harmful substances with high efficiency for a long period of time.

<Prior art> Typical examples of the above hydride-based waste gas include waste gas from the semiconductor manufacturing process. Conventional technologies for abating this semiconductor waste gas include, for example, Japanese Patent Laid-Open No. 60-125228-9.
In both publications, the concentration of pyrophoric silane gases such as monosilane, disilane, and trisilane contained in the waste gas is reduced by bringing the semiconductor waste gas into contact with a mixed solution of an alkaline substance and alcohol. A method is disclosed.

<Problems to be solved by the invention> However, the waste gas discarded from actual semiconductor manufacturing factories is a mixture of gases discharged from etching furnaces, CVD furnaces, diffusion furnaces, annealing furnaces, epitaxial furnaces, etc. It is a gas, and hydrides include silane-based gases as well as toxic gases such as arsine, phosphine, and diborane, and these hydride-based toxic gases are especially emitted in the exhaust gas from diffusion furnaces. It accounts for the majority of the gas composition.

As a result, when factory waste gas is treated with the mixed solution of the above-mentioned conventional technology, silane-based gas can be removed, but the removal rate of other hydride-based gases other than silane-based gas is low.
There is a problem that there is a big risk of air pollution.

The technical objective of the present invention is to appropriately eliminate hydride-based waste gases, which contain toxic gases such as arsine, phosphine, and diborane in addition to silane-based gases, in each composition.

Means for Solving the Problems> The present inventor has newly discovered that hydride-based harmful gases can be decomposed and removed using a mixed solution that basically consists of a small amount of an oxidizing agent and a large amount of alcohol. and completed the present invention.

That is, the present invention provides a method for abatement of hydride-based waste gas in which the waste gas containing hydride-based harmful gas is brought into contact with a treatment liquid to reduce the concentration of the harmful gas, in which the treatment liquid contains an oxidizing agent. It is characterized by being an alcohol solution containing.

The above hydride-based harmful gases include arsine, phosphine,
Including silane and diborane, germanium hydride,
It means one or more of selenium hydride, hydrogen sulfide, etc.

The above alcohols are: (1) aliphatic monovalent alcohols such as methyl, ethyl, propyl, butyl, amyl, hexyl or heptyl alcohol;
(2) Aliphatic polyhydric alcohols such as ethylene glycol, propylene glycol, butanediol, and glycerin (3) Alicyclic alcohols such as cyclohexanol and cyclopentanol (4) Phenol and benzyl alcohol , catechol,
It refers to aromatic alcohols such as hydroquinone, resorcinol, cresol, and salicylic acid, but it also refers to linear aliphatic (i.e., primary) alcohols selected from the group consisting of n-propyl alcohol, n-butyl alcohol, ethyl alcohol, and methyl alcohol. One type of alcohol or a mixture of alcohols is preferred.

In addition, the above-mentioned oxidizing agents include (1) nitrates such as silver nitrate, copper nitrate, potassium nitrate, or sodium nitrate (2) ferric chloride, copper sulfate (3) potassium permanganate, potassium dichromate, sodium chromate, peroxonitrile, etc. Refers to at least one of potassium sulfate, hydrogen peroxide, sodium peroxocarbonate, manganese dioxide, sodium perchlorate, sodium chlorate, sodium hypochlorite, potassium bromate, bleaching powder, etc.

The treatment liquid is obtained by mixing the oxidizing agent with an aqueous solution of the alcohol or anhydrous alcohol, and includes potassium permanganate, potassium dichromate, sodium chromate,
If a strong oxidizing agent such as potassium peroxodisulfate is mixed with alcohol before abatement treatment, a considerable portion of it will react with the alcohol and be reduced itself, which may reduce waste gas treatment efficiency. It is better to introduce the oxidizing agent and alcohol into the reaction tank from separate containers at the same time as introducing the waste gas into the reaction tank to carry out the decomposition reaction.

Therefore, as the oxidizing agent, silver nitrate, copper nitrate, ferric chloride, etc., which do not have any effect even if mixed with alcohol in advance, are preferable, and copper nitrate is more preferable from the viewpoint of cost.

In addition to alcohol and oxidizing agent, the processing liquid also contains, for example,
Sodium chloride may be added to stabilize the fine bubbles of waste gas dispersed in the processing solution, or pH adjusters, such as acids such as sulfuric acid may be added to improve potassium dichromate or potassium peroxodicarbonate. There is no problem in increasing the oxidation effect of

In addition, for actual abatement treatment, it is sufficient to use a normal gas-liquid contact device, but for example, a cup with the opening facing downward may be placed inside the reaction vessel and rotated, and the bottom end of the cup may be By ejecting the introduced waste gas into the processing liquid from countless nozzles made on the surface of the cup, the centrifugal effect based on the difference in specific gravity between the gas and liquid causes the gas layer to be torn off by the liquid, creating microbubbles in the liquid. If a rotating micro-bubble generator or the like is used for dispersion, the gas-liquid contact efficiency can be improved and the abatement treatment can be carried out effectively.

In a reaction system in which waste gas is brought into contact with a mixed solution consisting of an oxidizing agent and alcohol, some of the hydride-based harmful gases such as arsine, phosphine, silane, and diborane contained in the waste gas are first removed by the oxidizing agent. It can be assumed that it will be decomposed and removed.

In addition, for example, when nitric acid steel is used as the oxidizing agent, there is not much change in the removal rate even after copper precipitation.
In parallel with the above oxidative decomposition, the alcohol is converted by the oxidizing agent into an active substance such as percarboxylic acid, and this active substance acts on the toxic hydride (i.e., the alcohol and the oxidizing agent act synergistically). ), it can be assumed that a decomposition reaction occurs.

<Example> Hereinafter, based on FIG. 1, an outline of the abatement experiment device will be described, and an example of a detoxification experiment using the device will be shown.

The abatement experiment equipment consists of a reaction tank 1 and an abatement gas introduction line 2.
, a treated gas outlet line 3 , and a treated liquid circulation line 17 .

A predetermined processing liquid is contained in the reaction tank 1 having an internal volume of 100 g, and one end of the gas introduction line 2 to be removed is plunged into the processing liquid via a water ring vacuum pump 14.

The other end of the abatement target gas introduction line 2 is a hydride gas supply line 4 such as arsine or silane.

The hydride gas supply line 4 is connected to a hydride supply source 8 via an on-off valve 6 and a flow meter 7, and the N gas supply line 5 is connected to an on-off valve 10 and a flow meter 11. are connected to the gas supply source 12 via N, respectively.

One end of the processing liquid circulation line 17 is connected to the lower part of the reaction tank 1, and the other end is branched into two, with one end connected to the flowmeter 1.
8 to the inlet of the water seal pump 14, and the other end to the abatement target gas introduction line 2 via a flow meter 19.

Reference numeral 20 denotes a circulation pump, which circulates a part of the treatment liquid in the reaction tank 1 to the abatement target gas introduction line 2, and introduces the remainder of the treatment liquid into the water seal pump 14 to abate it inside the pump. The target gas and the treatment liquid are circulated through the introduction line 2 while being stirred and mixed to improve the removal efficiency.

In addition, a condenser 1 is connected to the treated gas derivation line 3.
5 is installed to condense the alcohol in the vaporized treatment liquid and reflux it to the reaction tank 1 as the temperature of the treatment liquid rises due to the heat of reaction, and an analyzer is installed at the tip of the derivation line 3. 16 (specifically, a gas chromatograph) to measure the residual concentration of the hydride in the treated gas.

Incidentally, in the abatement experiment, treatment liquids with various compositions and combinations of alcohol and oxidizing agent were stored in a reaction tank.
S i H,, A s H,, PH3 or B.

Continuing to flow the target gas containing H into each of the reaction tanks, measuring the residual concentration of hydrides in the gas outlet line,
The hydride removal rate in each treatment liquid was calculated.

Note that this removal rate was calculated based on the ratio of the residual ppm concentration in the output gas line to the ppm concentration of each hydride contained in the introduction gas line.

(Experimental Example 1) A treatment liquid 9012, which is a mixture of 87.5 vol. 1% n-propyl alcohol and copper nitrate (3.9 wt. .Qm3/
hr, and the inlet gas concentration is 50 to 3000p.
SiH gas, which was changed to pm (that is, diluted to the concentration with N gas), was flowed into the reaction tank 1, and the SiH4 concentration in the lead-out line 3 was measured.

Figure 2 is a chart showing the results, with 0.3m”/h
r, the removal rate is below the detection limit up to an inlet concentration of 500 ppm; 1. It can be seen that a removal rate of 99% or more can be ensured even at Qm'/hr, a large flow rate of 3000 ppm, and a high concentration.

Furthermore, when the flow rate exhibits a large value of 6.0 m'/hr, it can be seen that the lower the inlet concentration of SiH, the lower the removal rate, but even at an inlet concentration of 50 ppm, a removal rate of approximately 80% can be obtained.

(Experiment example 2) AsH using the same treatment solution as in Experimental Example 1 above.

The inlet concentrations of gas, pH, and gas were set at 50 ppm, and the respective flow rates were varied from 0.3 to 20.0 m3/hr, and the outlet gas concentrations of both gases were measured.

FIG. 3 is a chart showing the results, and it can be seen that the removal rate of PHs is below the detection limit at all flow rates.

In addition, the removal rate of ASH3 is 0.3 to 6.0 m'/h
At a flow rate of r, it is still below the detection limit, and lQm3/
98.0% at hr, 96 even at a large flow rate of 20 m'/hr
．． It can be seen that it is extremely practical as it shows 0%.

(Experimental Example 3) 1.0 wt% copper nitrate in 75.0 vol 1% methanol
A treatment liquid 9012 mixed at a ratio of is stored in a reaction tank l,
SiH with a gas flow rate of 1 m3/hr and an inlet gas concentration of 7.4 ppm, and with the same gas flow rate and an inlet gas concentration of 20 ppm.
Hydride gases such as AsH3, P Hs, and Bt He set at ppm were flowed into the reaction tank 1, and the outlet gas concentrations in the outlet line 3 were measured.

(Experimental Example 4) Using a treatment liquid with the following composition and setting the remaining elements to the same conditions as in Experimental Example 3, the outlet gas concentration was measured.

Methanol aqueous solution 75. Qvo1% copper nitrate
(3, Qwt% (Experimental Example 5) Using a treatment liquid with the following composition and setting the remaining elements under the same conditions as in Experimental Example 3, the outlet gas concentration was measured.

Methanol aqueous solution 75. Qvo1% copper nitrate
50.0wt% (Experimental Example 6) Using a treatment liquid with the following composition and setting the remaining elements to the same conditions as in Experimental Example 3, the outlet gas concentration was measured.

Methanol aqueous solution 75.0vo1% copper nitrate
(3.Qwt% Sodium chloride 2.Qwt% (Experimental Example 7) Using a treatment liquid with the following composition and setting the remaining elements to the same conditions as in Experimental Example 3 above, the outlet gas concentration was measured.

Methanol aqueous solution 75.0vo1% silver nitrate
5.3wt% (Experimental Example 8) Using a treatment liquid with the following composition and setting the remaining elements to the same conditions as in Experimental Example 3, the outlet gas concentration was measured.

Ethanol aqueous solution 82.0vo1% silver nitrate
5.3 wt% However, Comparative Example 1 is a mixture of 1 wt% NaOH added to 75 vol 1% methanol aqueous solution corresponding to the prior art described above, Comparative Example 2 is a 75 vol 1% methanol aqueous solution, and copper nitrate (3, Qwt% % aqueous solution as Comparative Example 3, the residual concentration of hydride gas was measured under the same conditions as in Experimental Examples 3 to 8 above, and a comparative experiment was conducted with the treatment liquid of the present invention.

FIG. 4 is a chart showing the results of Experimental Examples 3 to 8 above,
When the treatment solution is a combination of methanol and copper nitrate, increasing the amount of copper nitrate from 1, Qwt% to 6.0wt% causes S
i H,, A s H3, PH,, Bz) (The removal rate of s improves, but when copper nitrate is significantly increased to 50 wt%, the removal rate of each decreases (Experimental example 3 ~ 5
).

Furthermore, when sodium chloride is added to the treatment liquid, each removal rate is improved (see Experimental Example 4→Experimental Example 6).

On the other hand, when the oxidizing agent is changed from copper nitrate to silver nitrate and the alcohol is changed from methanol to ethanol, the removal rate also improves (see Experimental Example 4→Experimental Example 7 and Experimental Example 7→Experimental Example 8).

On the other hand, in the alcohol-only aqueous solution of Comparative Example 2,
Si)1. shows a low removal rate of approximately 33%.

Furthermore, in the aqueous solution of copper nitrate alone in Comparative Example 3, the removal rate of AsH3 was only 22.0%.

Furthermore, in the mixed solution of alkali and alcohol of Comparative Example 1 (that is, corresponding to the prior art mentioned above), the removal rate of SiH reached 95%, but the removal rate of AsHl reached 0.
7% and PH, it is only 3.0% (it can be seen that these hydrides can hardly be removed).

Therefore, it can be seen that in the detoxification method of the present invention, the alcohol and the oxidizing agent act synergistically to decompose hydride gases such as SiH, AsHs, and the like.

<Effects of the Invention> Not only silane gases, but also a wide range of hydride harmful gases such as arsine, phosphine, and diborane, which were difficult to remove with conventional alcohol and alkali mixed solutions, can be efficiently removed. , extremely practical for waste gas treatment from semiconductor manufacturing factories, etc.

Moreover, in the present invention, since harmful hydride gases can be effectively removed by membrane treatment, a multi-stage treatment is possible in which a plurality of treatment tanks filled with treatment liquids of different compositions are provided and waste gas is passed through these treatment tanks in turn. It is not necessary to perform this process, and the processing equipment can be simplified and implemented at low cost.

[Brief explanation of the drawing]

Fig. 1 is a schematic system diagram of the abatement experiment device of the present invention, Fig. 2 is a chart showing the results of abatement experiment example 1, and Fig. 3 is a diagram showing the results of abatement experiment example 2.
FIG. 4 is a chart showing the results of Harm Elimination Experimental Examples 3 to 8. 1...Reaction tank, 2...Abatement target gas introduction line, 3
... Treated gas derivation line, 4 ... Hydride gas supply line, 5 ... N, gas supply line, 14 ...
・Water ring vacuum pump, 15... Capacitor, 16...
・Analyzer, 17... Processing liquid circulation line, 20...
circulation pump. Patent applicant: Iwatani Sangyo Co., Ltd. Figure 2 Figure 3 Figure 4 0n-

Claims (1)

[Scope of Claims] 1. In a hydride-based waste gas abatement method in which waste gas containing hydride-based harmful gases is brought into contact with a treatment liquid to reduce the concentration of the harmful gas, the treatment liquid is oxidized. Method 2 for abatement of hydride-based waste gas, characterized in that the alcohol solution is an alcohol solution containing an alcohol, the alcohol being a linear alcohol selected from the group consisting of n-propyl alcohol, n-butyl alcohol, ethyl alcohol, and methyl alcohol. The oxidizing agent is a nitrate such as silver nitrate, copper nitrate, potassium nitrate or sodium nitrate; , ferric chloride, potassium permanganate, potassium peroxosulfate, sodium chlorate, sodium perchlorate, or potassium bromate. The method 4 for removing harm from hydride-based waste gas as described in Claim 3, wherein the treatment liquid is an n-propyl alcohol solution containing copper nitrate. Method 5: hydrogen according to any one of claims 1 to 4, wherein the hydride-based toxic gas is at least one of arsine, phosphine, silane, or diborane. Method 6 for abatement of chemical waste gas, a method for abatement of hydride waste gas according to any one of claims 1 to 5, characterized in that sodium chloride is added to the treatment liquid.