JPH07275646A - Harmful gas purifying agent - Google Patents

Abstract

PURPOSE:To obtain a purifying agent capable of efficiently removing harmful acidic gas such as boron trichloride, chlorine, hydrogen chloride, hydrogen bromide, boron trifluoride, tungsten hexafluoride or silicon tetrafluoride contained in exhaust gas discharged from a semiconductor manufacturing process. CONSTITUTION:A molded element using a compsn. based on triiron tetroxide and containing water is used as a purifying agent. At the time of molding, if necessary, an alumina carrier or sodium hydroxide or potassium hydroxide being a binder is added to the compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a toxic gas purifying agent, and more particularly to boron trichloride, chlorine, hydrogen chloride,
The present invention relates to a cleaner for acidic harmful gases such as hydrogen bromide and boron trifluoride, which are discharged mainly after being used in semiconductor manufacturing processes.

In recent years, along with the development of the semiconductor industry and optoelectronics industry, boron trichloride, chlorine, hydrogen chloride,
The types and amounts of halogen-based acidic gases such as hydrogen bromide, boron trifluoride, tungsten hexafluoride, silicon tetrafluoride, and chlorine trifluoride are increasing. These gases are indispensable substances for producing crystalline silicon, amorphous silicon or silicon oxide films, or as etching gas in the silicon semiconductor and compound semiconductor manufacturing industries, etc., but they are all highly toxic and are harmful to humans and the environment. Since they have an adverse effect, these harmful gases including acidic gas must be purified before being released into the atmosphere after being used in a semiconductor manufacturing process or the like.

Gases such as carbon tetrafluoride, perfluoropropane and sulfur hexafluoride, which have little hydrolyzability and relatively low toxicity, are also used for dry etching of silicon films and silicon oxide films in the semiconductor manufacturing process. In the gas discharged through the etching process, harmful gases such as silicon tetrafluoride and fluorine are generated by the reaction of these gases with the above-mentioned film components and the decomposition of the gas. In that case, purification is necessary.

[0004]

2. Description of the Related Art Conventionally, scrubbers have been used as means for removing acidic gases such as hydrogen chloride, hydrogen fluoride, boron trichloride, boron trifluoride and carbon tetrafluoride contained in gases.
A wet method of absorbing and decomposing these gases by contacting them with an alkaline aqueous solution such as sodium hydroxide using a spray tower, a rotary type fine bubble generator, etc. (JP-A-61-2040).
No. 22, JP-A No. 62-125827, etc.),
Adsorbents such as magnesium, sodium and potassium oxides and carbonates (JP-A-63-232844), and adsorbents in which a zinc compound and an alkali metal compound are impregnated with activated carbon (JP-A-60-68051). Alternatively, a dry method is known in which these harmful gases are passed through a filling cylinder filled with a solid substance such as a purifying agent containing soda lime as an active ingredient for purification.

[0005]

However, the wet method generally has a problem that post-treatment is difficult, the apparatus is complicated and large, and the equipment and maintenance are expensive. On the other hand, as a dry method, an adsorbent such as an oxide of magnesium, sodium, potassium, or a carbonate has a small removal capacity per unit volume of the adsorbent. Further, the adsorbent impregnated with activated carbon such as a zinc compound and an alkali metal compound or a purifying agent using soda lime cannot be said to have a sufficient removal capacity, and if the concentration of the acidic gas is high or the amount is large, Not only is there a problem that it cannot be sufficiently treated, but an adsorbent using activated carbon may generate an inflammable substance in a gas having a very high reactivity such as fluorine, which may cause a fire.

Further, soda lime has a deliquescent property, and there is a possibility that the purifying cylinder may be clogged by the water contained in the processing gas, and chlorine-based substances such as hydrogen chloride, chlorine and boron trichloride may be added. When the above gas is circulated, calcium chloride having a remarkable deliquescent property is generated, so that there is a problem that the kind of gas suitable for purification is limited. Therefore, the processing speed and the processing capacity of harmful gas are large, the removal performance is excellent for various acid gases that are usually discharged from the semiconductor manufacturing process, etc., and there is no risk of fire during purification,
Moreover, the advent of a purifying agent for harmful gas, which is not likely to cause clogging of the purifying cylinder due to deliquescence, has been desired.

[0007]

Means for Solving the Problems As a result of intensive studies to solve these problems, the present inventors have found that a molded body containing ferrosoferric oxide as a main component is used as a purifying agent. The present invention has been completed by discovering that the removal capability of the acid gas discharged from the semiconductor manufacturing process is extremely large and the removal process has high safety. That is, the present invention is a toxic gas purifying agent for removing an acidic gas from a gas containing an acidic gas as a toxic component, and is a molded product using a composition containing ferrosoferric oxide as a main component. It is a toxic gas purifier characterized by.

The purifying agent of the present invention is applied to purify acidic gas contained in exhaust gas discharged from a semiconductor process, mainly harmful gas containing halogen-based acidic gas. Hazardous gases to be purified include nitrogen, argon, helium, hydrogen, and air, which are usually halogen-based acidic gases such as chlorine, hydrogen chloride, dichlorosilane, silicon tetrachloride, phosphorus trichloride and trifluoride. Chloride, boron trichloride, boron trifluoride, tungsten hexafluoride, silicon tetrafluoride, fluorine, hydrogen fluoride, hydrogen bromide, etc., especially boron trichloride, chlorine, hydrogen chloride, bromide A gas containing one or more of hydrogen, boron trifluoride, tungsten hexafluoride, silicon tetrafluoride, and the like.

In the present invention, a composition containing triiron tetraoxide as a main component is used. Iron trioxide [Fe ₃ O ₄ ] is
For example, iron (II) hydroxide produced by blowing ammonia into iron (II) sulfate can be produced by oxidizing it with caustic soda and nitric acid, but a product having a purity of 95% or more is commercially available as iron black. Since it has been
Usually, these commercial products can be used.

In the present invention, it is preferable to add a proper amount of water to the purifying agent for the purpose of enhancing the ability to purify harmful gas. In this case, the content of water is usually 60% by weight or less as the content of the purifying agent after molding and preparation,
Preferably, it is about 5 to 40% by weight.

The composition containing ferrosoferric oxide as a main component may be molded as it is as a purifying agent, and a composition obtained by mixing a carrier material such as alumina, silica, alumina-silica, diatomaceous earth, etc. may be molded. It may be a purifying agent, or the composition may be carried on a carrier material that has been formed into a molded body in advance to serve as a purifying agent, but the composition as it is, or
A molded product obtained by mixing with a carrier substance and then extruding, tableting, or the like is preferable, and among them, a product obtained by directly molding the composition without using a carrier is particularly preferable.

At the time of molding, for the purpose of enhancing moldability and molding strength, sodium hydroxide, potassium hydroxide, sodium silicate (JIS
K1408) or these are preferably added and mixed together. The addition amount is determined according to the ratio of the components of the composition, molding conditions, etc., but is usually 0.1 to 20 parts by weight, preferably 0.5 to 10 parts by weight, based on 100 parts by weight of the composition. is there.

There are various methods for preparing the purifying agent. For example, a slurry or cake obtained by adding an aqueous solution in which a binder such as sodium hydroxide is dissolved to ferrosoferric oxide and stirring the mixture is extruded and molded, Pellets obtained by cutting into an appropriate length are dried in a drier to a specified water content and used as a cleaning agent, or the cake as described above is dried and then crushed, if necessary. There is a method of tableting a mixture obtained by adding and mixing a lubricant such as graphite, or a method of molding the cake into granules using a granulator or the like. Of these, workability and shape,
It is generally preferable to form a pellet by extrusion molding because the size can be easily selected.

There are no particular restrictions on the size and shape of the molded product, but typical examples include spherical, cylindrical, cylindrical and granular forms. If the size is spherical, the diameter is 0.
5 to 10 mm, diameter of 0.5 to 10 mm and height of 2 to 20 mm for pellets, tablets, etc., and 0.84 to 5 by opening of sieve for irregular shapes such as granules. It is about 66 mm. The packing density when the molded body is packed in the purification cylinder is usually 0.6 to 2.
It is about 0 g / ml.

The purifying agent of the present invention can be used not only as a fixed bed but also as a moving bed or a fluidized bed, but it is usually used as a fixed bed. The purifying agent is filled in the purifying cylinder, and the harmful gas containing the acidic gas is caused to flow into the purifying cylinder and brought into contact with the purifying agent to remove the acidic gas as the harmful component. The concentration of the acidic gas and the gas flow rate contained in the harmful gas to which the cleaning agent of the present invention is applied are not particularly limited, but generally, it is desirable to decrease the flow rate as the concentration increases. The concentration of the acid gas that can be removed is not particularly limited, but when the flow rate is small, it is possible to treat the acid gas having a high concentration of 10% or more.

The purifying column is designed according to the concentration of acidic gas, the amount of harmful gas to be purified, the allowable pressure loss, and the like. The filling length of the purifying agent in the purification column differs depending on the flow rate of gas and the concentration of harmful gas and cannot be specified unconditionally. However, in practice, it is usually about 50 to 1500 mm, and the inner diameter of the purification column is the gas flowing in the column. Is designed to have an empty cylinder linear velocity (LV) of about 0.01 to 150 cm / sec. Generally, these are determined by the pressure loss of the packed bed, the gas contact efficiency, the acid gas concentration, and the like.

The contact temperature is usually 0 to 90 ° C., preferably normal temperature (0 to 40 ° C.), and heating or cooling is not particularly required. After the contact is started, the temperature may slightly rise due to the reaction heat depending on the concentration of the acid gas, but there is no danger of ignition 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 increased pressure such as 1 kg / cm ² G.

The humidity of the harmful gas applied to the present invention is not particularly limited, and may be in a dry state or in a wet state as long as dew condensation does not occur. Note that the dry gas may have a reduced purification capacity depending on conditions such as temperature, flow rate, and heat generated by reaction with the cleaning agent.In such a case, gas that has been separately humidified at the inlet side of the cleaning tube is used. It is preferable to add moisture to the gas to be treated by supplying the gas.

[0019]

【Example】

Example 1 100 g of ferric oxide (Kanto Chemical Co., Inc., deer grade 1, purity 95% or more) was added to sodium hydroxide (Kanto Chemical Co., Ltd.,
A solution prepared by dissolving 2 g of deer (first grade, purity 95%) in 60 g of water was added and stirred. The obtained cake was extruded from a 1.6 mmφ nozzle plate by an extrusion molding machine (Fuji Paudal Co., Ltd.) to cut a molded product into pellets having a length of about 3 to 5 mm, and dried in a dryer at 80 ° C. for about 0.5 hours. After drying, 70 g of a cleaning agent was obtained. The water content of this product is 25% by weight, and the packing density is 1.2 g /
It was ml.

Example 2 A solution of 2 g of potassium hydroxide (Kanto Kagaku KK, deer grade 1, purity 85.5%) in 60 g of water was added to 100 g of ferric oxide, and the mixture was stirred. The obtained cake was extruded from a 1.6 mmφ nozzle plate by an extrusion molding machine to cut a molded product into pellets having a length of about 3 to 5 mm, and dried in a dryer at 80 ° C. for about 0.5 hours to give 58 g. The purifying agent was obtained. The water content of this product was 25% by weight, and the packing density was 1.1 g / ml.

Example 3 To 100 g of triiron tetraoxide, 60 g of water was added and stirred.
The obtained cake is 1.6mmφ by an extrusion molding machine.
3 ~ 5 length by cutting the molded product extruded from the nozzle plate of
58 g of a cleaning agent was obtained by making pellets of about mm and drying in a dryer at 80 ° C. for about 1 hour. Water content is 25% by weight, and packing density is 1.0 g / ml
Met.

Example 4 To 100 g of triiron tetraoxide, 60 g of 2 g of sodium hydroxide
The solution dissolved in water was added and stirred. The obtained cake was extruded from a 1.6 mmφ nozzle plate by an extrusion molding machine, cut into pellets having a length of about 3 to 5 mm, and dried at 80 ° C. for about 1 hour in a dryer to purify 60 g. An agent was obtained. The water content of this product was 8% by weight, and the packing density was 0.98 g / ml.

Example 5 Sodium silicate (JIS K) was added to 100 g of triiron tetraoxide.
1408, No. 3) 2 g in a solution of 60 g in water was added and stirred. The obtained cake was extruded from a 1.6 mmφ nozzle plate by an extrusion molding machine, and the molded product was cut into pellets having a length of 3 to 5 mm.
By drying at 0 ° C. for about 1 hour, 68 g of cleaning agent was obtained. The water content was 25% by weight, and the packing density was 1.16 g / ml.

Example 6 Pellets obtained as in Example 1 were dried in a drier 80
It dried at 6 degreeC for 6 hours, and obtained 50g of cleaning agents. This product had substantially no water and the packing density was 0.90 g / ml.

With respect to each of the purifying agents prepared in Examples 1 to 6, a purifying experiment of a gas containing an acidic gas was conducted. The purifying agent is put into a quartz glass purifying cylinder having an inner diameter of 19 mm and a length of 200 mm, and 28.4 ml of the purifying agent (filling length 100
mm) filled with nitrogen containing 1.0 vol% of various halogen-based acid gases at 20 ° C. and 170 at normal pressure.
A flow rate of ml / min (empty cylinder linear velocity LV = 1 cm / sec) was flown, the time until breakthrough was measured, and the amount of acid gas removed per 1 L of the cleaning agent was determined from this. To detect the breakthrough of the acidic gas, a part of the outlet gas of the purification column was sampled and measured using a chloride or fluoride detector tube (Gastec). The results for each type of purifying agent and gas are shown in Table 1.

[0026]

[Table 1] Table 1 Experiment number Type of acidic gas until breakthrough of acidic gas of purifying agent Type Time Removal amount (Example number) (Concentration 1%) (min) (L / L purifying agent) 1 Example 1 Boron trichloride 296 18 2 〃 Hydrogen chloride 280 17 3 〃 Hydrogen chloride 870 53 4 〃 Silicon tetrafluoride 329 20 5 〃 Tungsten hexafluoride 280 17 6 〃 Hydrogen bromide 511 31 7 7 〃 Trifluoroboron 23 8 Example 2 Boron trichloride 280 17 9 Example 3 〃 280 17 10 Example 4 〃 201 12 11 Example 5 〃 280 17 12 Example 6 〃 13 8

[0027]

Industrial Applicability The harmful gas purifying agent of the present invention has a large ability to remove acidic gases, and is effective in removing boron trichloride, chlorine, hydrogen chloride,
Since it is possible to efficiently remove acid gases such as hydrogen bromide, boron trifluoride, tungsten hexafluoride, and silicon tetrafluoride, the purification of harmful gases including acid gases emitted from semiconductor manufacturing processes, etc. An excellent effect can be obtained.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location B01D 53/34 134 A 134 C (72) Inventor Hideki Fukuda 5181 Tamura, Hiratsuka-shi, Kanagawa Japan Pionix Hiratsuka Laboratory Co., Ltd.

Claims (5)

[Claims] 1. A gas containing an acidic gas as a harmful component,
A toxic gas purifying agent for removing the acidic gas, wherein the toxic gas purifying agent is a molded product using a composition containing iron trioxide as a main component. 2. The purifying agent according to claim 1, wherein 60% by weight or less of water is contained in the entire purifying agent. 3. A molded product obtained by adding and mixing 0.1 to 20 parts by weight, based on 100 parts by weight of the composition, of at least one of sodium hydroxide, potassium hydroxide and sodium silicate as a binder. Purifying agent described in. 4. The acidic gas contained in the harmful gas is one or two of boron trichloride, chlorine, hydrogen chloride, hydrogen bromide, boron trifluoride, tungsten hexafluoride and silicon tetrafluoride. The purifying agent according to claim 1, which is the above. 5. The purifying agent according to claim 1, wherein the harmful gas is an exhaust gas discharged from a semiconductor manufacturing process.