KR0126123B1 - Process for cleaning harmful gas - Google Patents

Abstract

Harmful halogenated gases such as chlorine, hydrogen chloride, dichlorosilane, silicon tetrachloride, phosphorus trichloride, chlorine trifluoride, boron trichloride, boron trifluoride, tungsten hexafluoride, silicon tetrafluoride, fluorine, hydrogen fluoride and hydrogen bromide, A method of purifying a noxious gas for removing the halide by contacting with a purifying agent composed of zinc oxide, aluminum oxide and an alkali compound is disclosed.

This method is extremely effective in quickly and efficiently removing gaseous halides contained in a gas discharged from a semiconductor manufacturing process or a gas suddenly leaking from a gas cylinder.

Description

Hazardous Gas Purification Method

1 is a flow sheet showing a method for purifying harmful gas.

* Description of the symbols for the main parts of the drawings *

1: septic tank, 2: gas cylinder,

3: bomb box, 4: blower,

5: ventilation.

The present invention relates to a method for purifying a noxious gas, and more particularly, to a method for purifying a noxious gas of a halide type used in a semiconductor manufacturing process such as dichlorosilane, hydrogen chloride, and chlorine hexafluoride.

In recent years, with the development of the semiconductor industry and the optoelectronics industry, the types and amounts of halide gases such as hydrogen chloride, dichlorosilane, chlorine trifluoride and tungsten hexafluoride have increased.

These gases are used in the production of crystalline silicon, amorphous silicon, or silicon oxide films in silicon semiconductors, compound semiconductor manufacturing industries, or the like, or materials indispensable as etching gases, both of which are highly toxic and adversely affect the human body and the environment. Gases containing toxic gases need to be removed before being released into the atmosphere after use in semiconductor manufacturing processes.

In addition, hydrolyzable and relatively less toxic gases such as carbon tetrafluoride, propane fluoride, and sulfur hexafluoride are also used for dry etching of silicon films and silicon oxide films in semiconductor manufacturing processes. Due to the reaction between the water and the aforementioned membrane components or the decomposition of the gas, harmful components such as silicon tetrafluoride or fluorine are generated, and sufficient care must be taken when discharging the gas from the process.

On the other hand, these harmful gases are usually marketed by filling in a volume of 0.1-47L gas cylinder diluted with pure gas or nitrogen as shown below.

(Example of commercial gas filling cylinder)

In the use of these bombes, gas supply piping to a semiconductor process or the like is stored in a cylinder receiver connected to a ventilation box commonly referred to as a cylinder box in order to prevent direct contamination of external air in case of gas leakage. Used while connected to.

However, even when stored in a cylinder box, a thorough measure to cope with such an accident is strongly desired if a sudden accident or the like causes a rapid leak of emptying the cylinder in a short time of, for example, 5-10 minutes.

As a means for removing halide gases such as hydrogen chloride, dichlorosilane, and boron trifluoride, which are conventionally contained in the gas, a wet method of absorbing and decomposing with a scrubber, a purifier in which an alkali component is impregnated into a porous carrier such as activated carbon, and soda lime are effective. BACKGROUND OF THE INVENTION A dry method of purifying by flowing these fluid gases into a filling container filled with a purifying agent or the like as a component is known.

However, the wet method is generally disadvantageous in post-treatment and requires a maintenance cost of the apparatus.

On the other hand, as a dry method, the use of a purifier or soda lime impregnated with a porous carrier such as activated carbon with sodium hydroxide or potassium hydroxide is used quickly in case of an emergency when the removal rate and removal capacity are insufficient and the concentration of harmful gas is high or rapidly leaks. There is a problem that can not be processed.

In addition, a purifier using activated carbon as a carrier may cause a fire by generating a ignitable substance in an extremely reactive gas such as fluorine. In addition, soda lime is deliquescent and suitable for purification because calcium chloride, which is markedly deliquestable, is formed when the purification vessel is closed or chlorine gas such as hydrogen chloride or dichlorosilane is circulated depending on the moisture contained in the processing gas. There is a problem that the type of gas is limited.

Therefore, the processing speed and processing capacity of the harmful gas is large, and the concentration is relatively low due to the abnormality of the bomb. In addition, there has been a demand for the emergence of a purification method in which there is no danger of fire, etc. at the time of purification, and there is no possibility of closing of the container due to seawater.

The present inventors have diligently researched to solve these problems, and have found that by using a purifying agent containing zinc oxide, aluminum oxide and alkali compounds, it is possible to efficiently and safely remove harmful gases in various states. The present invention has been completed.

That is, the present invention is a method for purifying a noxious gas, wherein a gas containing a halide gas as a noxious component is contacted with a purifying agent composed of zinc oxide, aluminum oxide and an alkali compound to remove noxious components.

In the present invention, chlorine, hydrogen chloride, dichlorosilane, silicon tetrachloride, phosphorus trichloride, chlorine tetrafluoride, boron trichloride, boron trifluoride, tungsten hexafluoride, silicon tetrafluoride, fluorine, hydrogen fluoride contained in air, nitrogen and hydrogen Halogen-based harmful gases such as hydrogen bromide and the like can be produced with good efficiency.

In particular, not only the rapid purification (low concentration, large capacity) of the gas (usually air) polluted by the harmful gas rapidly discharged from the bomb as described above, but also the generally high concentration of harmful gas (high concentration, certain amount) discharged from the semiconductor process, etc. Excellent effects are obtained even under conditions in which the conventional method is difficult to purify.

The purifying agent used in the present invention is composed mainly of zinc oxide, aluminum oxide and an alkali compound.

As the zinc oxide, a commercially available one may be appropriately selected, or precursors such as zinc carbonate, basic zinc carbonate, zinc hydroxide and zinc organic acid, which may be changed to zinc oxide by firing, may be used.

As the aluminum oxide, alumina hydrate is usually used. For example, commercially available alumina sol or a high concentration alumina powdered thereof is suitable.

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

The amount of aluminum oxide and alkali compound with respect to zinc oxide is usually 0.02-0.06 atoms of aluminum, preferably 0.05-0.60 atoms with respect to 1 atom of zinc in atomic number ratio, and the amount of alkali compounds is usually alkali metal or ammonium 0.02-0.70 atoms, preferably 0.05-0.50 atoms.

Moreover, copper, chromium, iron, nickel, cobalt, etc. may be contained in small quantities as metal components other than zinc.

There are various methods for preparing the purifying agent, but for example, a mixture obtained by adding water to a mixture of an oxide of zinc or a precursor of an oxide and an alumina sol and an alkali compound, or drying the cake obtained by adding water to the precursor and alumina sol is dried. May be used as a purifying agent as it is or as a molded product.

In the case of using a purifying agent in a purifying container of a noxious gas or the like, it is preferable to mold and use a pellet.

There are various methods for molding, for example, a method of drying the pellets obtained by extrusion molding the cake of the mixture obtained above, a method of tableting molding the cake after drying and pulverizing, and adding and mixing a lubricant such as graphite thereto, or There is a method of granulating the cake using a granulator or the like.

Among them, it is generally convenient to form pellets by extrusion molding in terms of processability, shape, and size selection, and the pellets are preferably rounded at the tip using a rounding machine.

There is no particular limitation on the size and shape of the molded body, but spherical, cylindrical, cylindrical, etc. may be representatively mentioned.

Its size is 0.5-10mm in diameter for spherical shape, 0.5-10mm in diameter for cylindrical shape, and 2-20mm for height. If it is indefinite shape such as granular shape, the scale of 0.84-5.66mm is used as the scale of sieve.

The density of the molded body is usually in the range of 0.5-3.0 g / ml, preferably 0.7-2.5 g / ml.

In the present invention, the density refers to the weight of the molded body (particles) divided by the geometrical volume of the molded body.

In addition, the density in the case where the molded article is filled in the clarification container is 0.4-2.0 g / ml, Preferably it is about 0.5-1.5 g / ml.

In the present invention, the purifying agent can be used in a mobile phase or a fluidized phase, in addition to being used as a fixed phase.

Usually, the purifying agent is filled in the purifying container, and the gas containing the halide gas flows into the purifying container and is connected to the purifying agent to remove the harmful halides.

There is no particular restriction on the concentration and flow rate of the halide gas contained in the treatment target gas to which the purifying method of the present invention is applied, but in general, when the concentration is high, the flow rate may be reduced.

The concentration of the harmful gas that can be removed is usually 1% or less. However, when the flow rate is small, a high concentration of halogen gas can be treated.

The septic tank is designed according to the concentration of harmful gas and the amount of gas to be treated, but at relatively low concentrations such as the concentration of harmful gas is 0.1% or less, the linear linear velocity (LV) is 0.3-1.5m / sec and the concentration of harmful gas is 0.1-1%. In terms of accuracy, it is recommended to design the LV in the range of 0.05m / sec or less at high concentrations of 0.05-0.3m / sec and harmful gas concentration of 1% or more. Thus, for example, LV is 0.3-1.5 m / sec when noxious gas leaks rapidly from the gas cylinder and is diluted with a large amount of air. sec is the general standard.

The contact temperature is usually operated at 0-90 ° C., preferably at room temperature (10-50 ° C.) and does not require heating or cooling in particular.

In addition, after the start of contact, the temperature may increase slightly depending on the concentration of the harmful gas due to the heat of reaction, but there is no risk of ignition because no combustibles such as activated carbon are used.

The pressure at the time of contact is usually normal pressure, but can also be operated under pressure such as reduced pressure to 1 kg / cm ² G.

There is no particular limitation on the humidity of the harmful gas to which the method of the present invention is applied, and even if it is in a dry state or a wet state, as long as it does not cause condensation, there is no fear of causing dissolution or deterioration of the purifying agent.

It also does not adversely affect the carbon dioxide gas in the air.

In the present invention, for example, when a sudden leakage of noxious gas in the cylinder box is assumed, as shown in the flow sheet of FIG. 1, the purification tank 1 is a cylinder box 3 in which the gas cylinder 2 is housed. It is in the state interposed in the ventilation cylinder 5 connected to the blower 4 for continuous suction ventilation of the air inside.

Such equipment is usually provided with a blower sufficient to mix with air and dilute its concentration to 1% or less even if a rapid leakage of harmful gas occurs.

Specifically, a blower with a ventilation capacity of about 5-200 m ³ / min is generally installed. The content of harmful gases such as air is considered to be about 50-1000 ppm.

The length of purifying agent in the septic tank depends on the flow rate of the gas and the concentration of toxic gas, so it can't be erased consistently, but it is usually about 50-500mm in practical use, and the inner diameter of the septic tank is 0.3-1.5m / It is designed to be about the size of sec.

Generally these are determined by the pressure loss of the packed bed, the contact efficiency of the gas and the concentration of the noxious gas.

According to the method for purifying the noxious gas of the present invention, it is possible to remove a large amount of noxious gases such as hydrogen chloride, dichlorosilane, tungsten hexafluoride and chlorine trifluoride at a relatively high concentration with good efficiency and very quickly. Not only an excellent effect is obtained for the purification of the high concentration of harmful gases discharged from the process and the like, but also an excellent effect is also obtained for the purification of a large amount of harmful gases in an emergency such as rapid leakage from a gas cylinder.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1-13

500 g of basic carbonaceous acid salt, high concentration of alumina (catalyst AP, Cataloid AP) 52.4 g (Al is 0.16 atom for 1 atom of Zn), anhydrous potassium carbonate 30.2 g (K is 0.10 for 1 atom of Zn) Atom) was put in a small kneader and mixed for 3 minutes, and then 280 g of water was mixed and kneaded for 1 hour. This cake is made by mini extruder 1.9 The pellet obtained by extruding with the nozzle plate of was rounded by a rounding machine, and dried at 110 degreeC for 2 hours. This was put into a furnace and calcined at 350 ° C for 1 hour to obtain a purifying agent having a density of 1.14 g / ml.

Using this purifier, the concentration was relatively low, as in the case of rapid leakage of harmful gas from the bomb, but the purification experiment was carried out in consideration of the large amount of harmful gas.

A 28.4 ml purifier (0.98 g / ml) was charged into a quartz glass purifier with an internal diameter of 19 mm and a length of 200 mm, containing 10 ppm of nitrogen containing 1000 ppm of various halide gases and 10.22 L / min under normal pressure (LV = 60 cm). / sec) flow rate.

The break through point was measured using a detection tube for chloride or fluoride (manufactured by GASTECH Co., Ltd.) by extracting a part of the outlet gas of the septic tank.

The results are shown in the first table.

[Table 1]

[Example 14-26]

Next, a high concentration and a certain amount of harmful gas discharged from the semiconductor process was assumed to be a harmful gas and the purification experiment was carried out.

Purification tanks as in Example 1 were prepared for nitrogen containing 1 vol% of various halide gases, respectively, and flowed at a flow rate of 850 ml / min (LV = 1 cm / sec) at 20 ° C. and atmospheric pressure, and was carried out as in Examples 1-13. The time to destruction was measured.

The results are shown in the second table.

[Table 2]

Comparative Example 1-8

Activated carbon was used as a carrier, which was impregnated with 40 wt% of sodium hydroxide and dried at 120 ° C. to 10 wt%, and the other was hydrogen chloride as in the examples, using a purifier impregnated with 50 wt% of potassium hydroxide. And dichlorosilane removal experiments.

The former is shown as Comparative Example 1-4 and the latter as Comparative Example 5-8, and the results are shown in Table 3.

[Table 3]

Claims (8)

A method for purifying a noxious gas, characterized by removing a noxious component by contacting a gas containing a halide gas as a noxious component with a purifier composed of zinc oxide, aluminum oxide and an alkali compound. The method of claim 1, wherein the halide gas is chlorine, hydrogen chloride, dichlorosilane, silicon tetrachloride, phosphorus trichloride, chlorine trifluoride, boron trichloride, boron trifluoride, tungsten hexafluoride, silicon tetrafluoride, fluorine, hydrogen fluoride and Method for purifying harmful gas which is at least one of hydrogen bromide. The method of claim 1, wherein the alkali compound is any one or more of potassium carbonate, potassium bicarbonate, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonium hydroxide. The method for purifying a toxic gas according to claim 1, wherein the mixing ratio of aluminum oxide and alkali compound to zinc oxide is 0.02-0.60 atoms with respect to 1 atom of zinc and 0.02-0.70 atoms with alkali metal or ammonium group as 1 atom. The method of claim 1, wherein the aluminum oxide is alumina hydrate. The method of claim 1, wherein the noxious gas is discharged from the semiconductor process. The method of claim 1, wherein the noxious gas leaks from the gas cylinder and is diluted with air. The method of claim 1, wherein the concentration of the noxious gas is 50-100% by volume.