JP3073321B2 - How to purify harmful gases - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for purifying harmful gases, and more particularly to a method for purifying harmful gases such as dichlorosilane, hydrogen chloride, tungsten hexafluoride and chlorine trifluoride which are used in a semiconductor manufacturing process. It relates to a gas purification method. In recent years, along with the development of the semiconductor and optoelectronic industries, hydrogen chloride, dichlorosilane, chlorine trifluoride,
The types and usage of halide gases such as tungsten hexafluoride are increasing. These gases are used to produce crystalline silicon, amorphous silicon, or silicon oxide films in the silicon semiconductor and compound semiconductor manufacturing industries, and are indispensable substances as etching gases. Gases containing these toxic gases must be removed of harmful components before they are released into the atmosphere after use in semiconductor manufacturing processes, etc., because they have a bad influence on the environment.

In addition, hydrolytic and relatively toxic gases such as carbon tetrafluoride, perfluoropropane and sulfur hexafluoride are also used for dry etching of silicon films and silicon oxide films in semiconductor manufacturing processes. Since harmful components such as silicon tetrafluoride and fluorine are generated in the gas discharged through the etching process due to the reaction between these gases and the above-mentioned film components and the decomposition of the gas, Great care must be taken. On the other hand, these harmful gases usually have a volume of 0.1 to 47 as exemplified below.
L gas cylinders are commercially available after being filled in a state diluted with pure gas or nitrogen or the like. (Example of a commercially available gas-filled cylinder) Gas name Cylinder capacity Concentration Filling weight (L) (%) (kg) HCl 47 100 25 SiH ₂ Cl ₂ 10 100 10 When using these cylinders, if gas leaks, In order to prevent direct contamination of the outside air, it is usually used in a form connected to a gas supply pipe to semiconductor processes etc. while being housed in a cylinder housing connected to a ventilation duct called a cylinder box. Can be However, even if it is stored in the cylinder box, there is no danger of sudden leakage such as emptying of the cylinder in a short time of about 5 to 10 minutes due to an unexpected accident or the like. There is a strong demand for thorough measures that can cope with serious accidents.

[0003]

2. Description of the Related Art Conventionally, as a means for removing a halide gas such as hydrogen chloride, dichlorosilane or boron trifluoride contained in a gas, a wet method in which a gas is absorbed and decomposed by a scrubber and a porous method in which an alkali component is activated carbon or the like are used. A dry method is known in which these harmful gases are passed through a packed cylinder filled with a purifying agent impregnated in a porous carrier, a purifying agent containing soda lime as an active ingredient, and the like, for purification.

[0004]

However, the wet method has a drawback in that the post-treatment is generally difficult and the maintenance cost of the apparatus is required. On the other hand, as for the dry method, the removal rate and removal capacity are not necessarily sufficient for those using a purifying agent or soda lime in which a porous carrier such as activated carbon is impregnated with sodium hydroxide, potassium hydroxide, etc. However, there is a problem that it is not possible to promptly deal with an emergency such as high cost or sudden leakage. Also,
A purifying agent using activated carbon as a carrier may generate an ignitable substance with extremely reactive gas such as fluorine, which may cause a fire. Furthermore, soda lime has deliquescence, and the moisture contained in the processing gas may cause clogging of the purification column, and furthermore, when chloride gas such as hydrogen chloride or dichlorosilane is allowed to flow. However, there is a problem in that the type of gas suitable for purification is limited because of the formation of highly deliquescent ruthenium chloride. Therefore, the processing speed and processing capacity of the harmful gas are large, and the concentration is relatively low due to abnormality of the cylinder, but not only in an emergency such as leakage of a large amount of gas, but also the high concentration discharged from the semiconductor manufacturing process is usually high. It has been desired to develop a purification method that has excellent removal performance for any harmful gas and the like, has no risk of fire or the like during purification, and has no risk of blockage of the purification column due to deliquescence.

[0005]

The present inventors have made intensive studies to solve these problems, and as a result, by using a purifying agent containing zinc oxide, aluminum oxide and an alkali compound, various methods have been proposed. It has been found that harmful gases in the state can be removed very efficiently and safely, and the present invention has been completed. That is, the present invention
A method for purifying a harmful gas, which comprises contacting a gas containing a halide gas as a harmful component with a purifying agent composed of zinc oxide, aluminum oxide and an alkali compound to remove the harmful component. The present invention relates to chlorine, hydrogen chloride, dichlorosilane, silicon tetrachloride, phosphorus trichloride, chlorine trifluoride, boron trichloride, boron trifluoride, tungsten hexafluoride, tetrachloride contained in air, nitrogen, and hydrogen. Halide-based harmful gases such as silicon fluoride, fluorine, hydrogen fluoride and hydrogen bromide can be efficiently removed. In particular,
Not only rapid purification (low concentration, high flow rate) of gas (usually air) contaminated by harmful gas such as rapid leakage from the cylinder as described above, but also generally high concentration discharged from a semiconductor process. Hazardous gas (high concentration, constant flow)
Excellent effects can be obtained even under conditions where purification by conventional methods is difficult.

The purifying agent used in the present invention contains zinc oxide, aluminum oxide and an alkali compound as main components. As the zinc oxide, an appropriate one may be selected from among commercially available products, and a precursor such as zinc carbonate, basic zinc carbonate, zinc hydroxide and organic acid zinc which can be converted to zinc oxide by firing or the like is used. You may. As the aluminum oxide, alumina hydrate is usually used, and for example, commercially available alumina sol or high-concentration alumina obtained by powdering the same is suitable. Further, examples of the alkali compound include hydroxides, carbonates and acetates of alkali metals such as lithium, sodium and potassium, alkaline earth metals such as magnesium and calcium, and ammonium. Of 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 compound relative to zinc oxide is
Usually, 0.02 to 0.60 atom of aluminum, preferably 0.05 to 0.6 atom, relative to 1 atom of zinc in atomic ratio.
0 atom, and the amount of the alkali compound is usually 0.02 to 0.70 atom, preferably 0.05 to 0.50 atom in an alkali metal or ammonium group. Further, a material containing a small amount of copper, chromium, iron, nickel, cobalt, or the like as a metal component other than zinc may be used.

There are various methods for preparing a purifying agent. For example, water is added to a mixture of zinc oxide or a precursor of the oxide and an alumina sol and an alkali compound and kneaded, or the precursor is mixed with an alumina sol. The cake obtained by adding water to water may be used as a purifying agent as it is, or may be used as a molded product. When the purifying agent is used by filling it in a harmful gas purifying column or the like, it is preferable to use the purifying agent by molding it into a pellet or the like. There are various molding methods, for example, extruding the cake of the mixture obtained above, molding the obtained pellets, drying the cake, pulverizing the cake after drying, adding a lubricant such as graphite to this, Tablet molding method of the mixture,
Alternatively, there is a method in which the cake is granulated using a granulator or the like. Of these, it is common and convenient to extrude and form pellets because of workability and shape, ease of selection of size, etc., and pellets are rounded at the tip using a marmellaizer etc. Is preferred.

[0008] The size and shape of the molded body are not particularly limited, but spheres, columns, cylinders and the like are typical examples. If the size is spherical, the diameter is 0.5 ~
If the diameter is 10 mm, the diameter is about 0.5 to 10 mm and the height is about 2 to 20 mm in the case of a cylindrical shape, and the diameter is about 0.84 to 5.66 mm in the case of an irregular shape such as a grain. Things are used. The density of the compact is usually 0.5
-3.0 g / ml, preferably 0.7-2.5 g / ml
Range. In the present invention, the density refers to a value obtained by dividing the weight of a compact (grain) by the geometric volume of the compact. Also, the density when the molded body is filled in a purification column is usually 0.4 to
It is about 2.0 g / ml, preferably about 0.5 to 1.5 g / ml.

In the present invention, the purifying agent can be used not only as a fixed bed but also as a moving bed or a fluidized bed. Normally, a purifying agent is filled in a purifying column, and a gas containing a halide gas is flowed into the purifying column, and the harmful component halide is removed by bringing the gas into contact with the purifying agent. The concentration and flow rate of the halide gas contained in the gas to be treated to which the purification method of the present invention is applied are not particularly limited, but it is generally desirable that the higher the concentration, the lower the flow rate. The concentration of the harmful gas that can be removed is usually 1% or less, but when the flow rate is small, a higher concentration of the halogen gas can be treated. The purifier is designed according to the concentration of harmful gas, the amount of gas to be treated, etc.
The cylinder linear velocity (LV) is 0.3 to 1.5 m / sec when the harmful gas concentration is relatively low such as 0.1% or less, and the LV is 0 when the harmful gas concentration is about 0.1 to 1%. .05-0.
At a high concentration such as 3 m / sec and a concentration of 1% or more, LV
Is preferably designed within a range of 0.05 m / sec or less. Therefore, for example, when harmful gas leaks rapidly from the gas cylinder and is diluted with a large amount of air, etc.
V is 0.3 to 1.5 m / sec, and is 0.0 in the case of high concentration harmful gas constantly discharged from the process.
5 to 0.3 m / sec is a general standard. The contact temperature is usually 0 to 90 ° C, preferably normal temperature (10 to 50 ° C)
It does not require heating or cooling. After the start of contact, the temperature of the harmful gas may increase slightly depending on the concentration of the harmful gas due to the heat of reaction, but there is no danger of ignition or the like because no combustible material such as activated carbon is used. The pressure at the time of contact is usually normal pressure, but it is also possible to operate under reduced pressure or under pressure such as 1 kg / cm ² G. The humidity of the harmful gas to which the method of the present invention is applied is not particularly limited as long as it does not cause dew condensation even in a dry or wet state, and there is no possibility of deliquescent or deterioration of the purifying agent. Also, there is no particular adverse effect due to carbon dioxide in the air.

In the present invention, for example, when it is assumed that a harmful gas leaks in a cylinder box, FIG.
As shown in the flow sheet of FIG. 1, a ventilation duct 5 connected to a blower 4 for continuously sucking and ventilating air in a cylinder box 3 containing a gas cylinder 2 is provided.
It is performed in a state where it is interposed. Such equipment is usually provided with a blower sufficient to reduce the concentration of harmful gas to 1% or less by mixing with air even if a sudden leak of harmful gas occurs. Specifically, a blower having a ventilation capacity of about 5 to 200 m ³ / min is generally installed. For example, a commercially available gas cylinder shown in the above table becomes empty in 5 to 10 minutes. When such a leak occurs, the content of harmful gas such as in air is
It is assumed to be around 50-1000 ppm. The filling length of the purifying agent in the purifying cylinder differs depending on the flow rate of the gas and the concentration of the harmful gas and cannot be specified unconditionally. However, in practice, it is usually about 50 to 500 mm, and the inner diameter of the purifying cylinder is the gas flowing through the cylinder. The cylinder linear velocity (LV) is 0.3 to 1.5
It is designed to have a size of about m / sec. Generally, these are determined by the pressure loss of the packed bed, the gas contact efficiency, the concentration of harmful gas, and the like.

[0011]

【Example】

Examples 1 to 13 500 g of basic zinc carbonate, 52.4 g of high-concentration alumina (catalyst AP, manufactured by Catalysis Kasei Co., Ltd.) (0.16 atom of Al per atom of Zn), anhydrous potassium carbonate 3
0.2 g (K is 0.10 atom per atom of Zn) was put in a small kneader and mixed for 3 minutes, and then 280 g of water was added and kneaded for 1 hour. The cake was extruded from a 1.9φ nozzle plate by a small extruder, and the pellets obtained were rounded by a marmellaizer and dried at 110 ° C. for 2 hours. This was put in a muffle furnace and calcined at 350 ° C. for 1 hour to obtain a purifying agent having a density of 1.14 g / ml.

Using this purifying agent, a purifying experiment was first conducted on the assumption that a large amount of a harmful gas, although the concentration was relatively low as when a harmful gas leaked rapidly from a cylinder. Purification agent 28.4 ml (filling density 0.98 g / ml)
mm and a 200 mm long quartz glass purifying cylinder, into which nitrogen containing 1000 ppm of various halide gases is added at 20 ° C. and normal pressure at 10.22 L / min.
(Cylinder linear velocity LV = 60 cm / sec). The breakthrough was detected by sampling a part of the outlet gas of the purifying column and using a chloride or fluoride detector tube (Gastec). Table 1 shows the results.

[0013]

Table 1 Example 1 Harmful gas Harmful gas Void linear velocity Effective treatment time Type concentration LV (ppm) (cm / sec) (min) 1 Hydrogen chloride 1000 60 112 2 Dichlorosilane 1000 60 45 3 Trichloride Boron 1000 60 20 4 Silicon tetrachloride 1000 60 265 Chlorine 1000 60 42 6 Silicon tetrafluoride 1000 60 237 Phosphorus trichloride 1000 60 238 Fluorine 1000 60 97 9 9 Chlorine trifluoride 1000 60 49 10 Tungsten hexafluoride 1000 60 23 11 Hydrogen bromide 1000 60 83 12 Hydrogen fluoride 1000 60 40 13 Boron trifluoride 1000 60 25

Examples 14 to 26 Next, a purification experiment was performed assuming a high-concentration, constant-flow harmful gas discharged from the semiconductor process. For nitrogen containing 1 vol% of various kinds of halide gases, the same purifying column as in Example 1 was prepared and circulated at 20 ° C. and normal pressure at a flow rate of 850 ml / min (LV = 1 cm / sec). The time until breakthrough was measured in the same manner as in Examples 1 to 13. Table 2 shows the results.

[0015]

Table 2 Example Hazardous gas Hazardous gas Void linear velocity Effective treatment time Concentration LV (%) (cm / sec) (min) 14 Hydrogen chloride 15 241 15 Dichlorosilane 15 80 16 Trichloride Boron 1 55 17 17 Silicon tetrachloride 15 55 18 Chlorine 15 25 19 Silicon tetrafluoride 15 33 20 Phosphorus trichloride 15 52 21 Fluorine 15 55 156 22 Chlorine trifluoride 15 37 23 23 Tungsten hexafluoride 1 5 64 24 Hydrogen bromide 15 196 25 Hydrogen fluoride 15 89 26 Boron trifluoride 15 80

Comparative Examples 1 to 8 Activated carbon was used as a carrier, and sodium hydroxide was added to the carrier.
hydrogen chloride and dichlorosilane in the same manner as in the example, using a purifying agent impregnated with wt% and dried at 120 ° C. to a water content of 10 wt%, and another purifying agent obtained by impregnating activated carbon with 50 wt% of potassium hydroxide. A removal experiment was performed. The former is Comparative Examples 1-4 and the latter is Comparative Examples 5-8
Table 3 shows the results.

[0017]

Table 3 Comparative Example Hazardous gas Hazardous gas Void linear velocity Effective treatment time Type concentration * LV (cm / sec) (min) 1 Hydrogen chloride 15 2 Dichlorosilane 15 5 Hydrogen chloride 500 60 12 4 Dichlorosilane 500 60 8 5 Hydrogen chloride 1.56 Dichlorosilane 1557 Hydrogen chloride 500 60 18 8 Dichlorosilane 500 60 12 (* Units of concentration are 1, 3, 5, 6 are%, 3, 4, 7, 8) Is ppm)

[0018]

According to the method for purifying harmful gas of the present invention,
A relatively high concentration of a large amount of halide-based harmful gases such as hydrogen chloride, dichlorosilane, tungsten hexafluoride, and chlorine trifluoride can be removed efficiently and extremely quickly. Not only is it effective in purifying high-concentration harmful gas emissions,
For example, an excellent effect can be obtained for purifying a large amount of harmful gas in an emergency such as a sudden leak from a gas cylinder.

[0019]

[Brief description of the drawings]

FIG. 1 is a flow sheet showing a method for purifying harmful gases.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Purification cylinder 2 Gas cylinder 3 Cylinder box 4 Blower 5 Ventilation duct

Continuation of the front page (56) References JP-A-2-43917 (JP, A) JP-A-2-75318 (JP, A) JP-A-3-40901 (JP, A)

Claims (4)

(57) [Claims] 1. A harmful gas comprising removing a harmful component by contacting a gas containing a halide gas as a harmful component with a purifying agent comprising zinc oxide, aluminum oxide and an alkali compound. Purification method. 2. The method according to 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. The purification method according to claim 1, wherein the purification method is one or more selected from hydrogen fluoride, hydrogen fluoride, and hydrogen bromide. 3. The method according to claim 1, wherein the alkali compound is one or more selected from potassium carbonate, potassium bicarbonate, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium hydroxide and ammonium hydroxide. Purification method. 4. The mixing ratio of aluminum oxide and alkali compound to zinc oxide is 0.02 to 0.60 atom for one atom of zinc and 0.02 to 0.70 atom for one atom of alkali metal or ammonium group. 2. The purification method according to claim 1, wherein the purification method is an atom.