JP2604991B2 - Exhaust gas treatment agent - 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 of treating an exhaust gas containing an inorganic group V compound such as phosphine or arsine discharged from a manufacturing process of a group III-V compound semiconductor thin film by a chemical reaction, thereby obtaining an inorganic group V compound in the exhaust gas. The present invention relates to a treating agent for detoxifying and removing a compound.

[0002]

2. Description of the Related Art Group-III-V compound semiconductor thin films such as gallium arsenide are important as materials for manufacturing electronic devices because of their fast electron transfer, low power consumption, and good luminous efficiency. As a method of forming a thin film of a compound semiconductor, (A) MOCVD (Metal Org)
anic Chemical Vaporphase D
(E), (B) MOVPE (Metal
Organic Vapor Phase Epit
axy), (C) MBE (Mole-cular Be)
am Epitaxy) and (D) halide CVD. Among them, (A) MOCVD and (B) MOV
PE is a crystal growth method that has attracted much attention because it is not necessary to maintain a high vacuum in the crystal chamber, and it is easy to exchange raw materials and easy to maintain.

[0003] In these crystal growth methods, a conventional II
Organometallic compounds such as trimethylaluminum and triethylindium have been used as Group I raw materials, and phosphine and arsine, which are inorganic hydrides, have been used as Group V raw materials. The low proportion of these inorganic hydrides, phosphine and arsine, fixed to the crystal, and III
Group V raw materials are used in large amounts with respect to Group raw materials,
A considerable amount of inorganic hydrides, phosphine and arsine, accompany the exhaust gas. As is well known, phosphine and arsine are highly toxic and require treatment of exhaust gas.

These group III organometallic compounds and inorganic V
As a treatment agent for exhaust gas from a III-V compound semiconductor thin film manufacturing process using a group compound, a treatment agent containing copper oxide as a main component or a material obtained by impregnating a caustic alkali solution with silicate earth or the like is used as a main component. A stainless steel container is filled with a treating agent to be used and a cartridge type is practically used. These dry treatment methods have been found to be effective in treating inorganic group V hydrides such as phosphine and arsine contained in exhaust gas. Another advantage is that the cartridge can be easily replaced.

[0005] On the other hand, as a wet treatment method, there is a method in which a solution containing silver nitrate, silver perchlorate, a water-soluble copper compound or caustic alkali is sprayed or allowed to flow into a packed tower to contact exhaust gas. MOCVD and M
It is not applicable except in special cases due to the risk of back diffusion and back flow into the OVPE device body and piping. V, which is the molar ratio between the inorganic group V compound and the group III compound supplied to the crystal growth chamber
The / III ratio is an important control factor that affects the properties of the compound semiconductor thin film, and the actual operation value is as high as 10 to 1000, and the group V compound is overwhelmingly used for the group III compound. You. Therefore, the composition of the exhaust gas from the manufacturing process of the compound semiconductor thin film in the MOCVD or MOVPE method is that most of the components to be harmed other than the carrier gas, which is the main component, are caused by the group V compound, that is, phosphine and arsine. Almost no harmful substances caused by group III compounds are contained.

[0006]

The treating agent containing copper oxide as a main component utilizes a chemical reaction in which phosphine or arsine, which is an inorganic group V compound, reacts with copper oxide to form copper phosphide or copper arsenide. To remove phosphine and arsine. The chemical reaction between copper oxide and an inorganic group V compound is an exothermic reaction. When the exhaust gas from the compound semiconductor thin film manufacturing process is treated with a cartridge filled with a treating agent containing copper oxide as a main component, the temperature of the cartridge outer wall becomes abnormal. Has the disadvantage of rising. This causes various adverse effects, so that it is necessary to particularly strengthen safety measures. In order to avoid local heating, a method of diluting the concentration of copper oxide has been adopted. If the diluent used at this time has an adsorption ability and the specific surface area is too large, there is a risk that the inorganic group V compound is desorbed from the diluent after the exhaust gas treatment and leaks out of the system. Such diluents include activated alumina, activated carbon and zeolites. Also,
The diluent has a large pore size and a large number of diluents so that the transfer and diffusion of the inorganic group V compound in the exhaust gas can be accelerated in order to compensate for the reduction in the abatement ability due to the decrease in the concentration of copper oxide in the treating agent. There is a need.

[0007] If the treating agent is powdered at the time of filling the cartridge or during the treatment of the exhaust gas, local heating is caused by the drift of the exhaust gas, which causes not only a decrease in the abatement capacity of the treating agent but also a decrease in the pressure of the abatement tower. Due to the increased losses, the treating agent must be strong enough to maintain its shape. Further, in order to prevent dust generation during the molding of the treatment agent, it is necessary to improve the moldability of the basic copper carbonate, and as a means therefor, there is a method of adding an adhesive organic binder. However, in this method, there is a disadvantage that the organic binder coats the basic copper carbonate to lower the solid-gas contact, thereby lowering both the efficiency and capacity of the removal.

When the treating agent containing copper oxide as a main component and the inorganic group V compound react with each other, the volume shrinks due to heat, so that the state of filling of the treating agent changes and affects the gas flow. Further, since the volume shrinkage starts from the surface of the treatment agent, the surface structure is densified, so that the internal copper oxide is not effectively used, and as a result, the abatement ability of the treatment agent is reduced.

The present invention solves the above problem in the treatment of exhaust gas containing an inorganic group V compound such as phosphine and arsine discharged from a manufacturing process of a group III-V compound semiconductor thin film. In doing so
As a whole, heat generation is small and processing can be performed safely.
An object of the present invention is to provide an exhaust gas treating agent which is excellent in moldability, has good solid-gas contact, makes effective use of copper oxide, and has a high detoxification ability.

[0010]

Means for Solving the Problems The inventor of the present invention has proposed a method for solving the above-mentioned problems, such as MOCVD and MOVPE.
As a result of searching for an effective component for treating the inorganic V compound contained in the exhaust gas discharged from the group V compound semiconductor thin film manufacturing process, basic copper carbonate is effective for detoxifying the inorganic V compound, In addition, basic copper carbonate is thermally decomposed into copper oxide, but heat of decomposition is an endothermic reaction.
It has been found that the heat of reaction with the group compound can be absorbed and the heat generation as a whole can be suppressed.

Further, when anatase type fine particle titanium oxide is added as a diluent, the reaction between the inorganic group V compound and the basic copper carbonate can be efficiently performed by the relatively large specific surface area and the large diameter pores. The anatase-type fine particle titanium oxide does not react with the inorganic group V compound itself, but has the effect of reducing the calorific value per unit volume by adding it, and moreover, when the exhaust gas passes through the packed tower, It has been found that, in order to reduce the pressure loss, the processing agent is improved in the formability and the strength of the molded product when it is formed into an appropriate size and shape.

Based on this finding, the present invention provides
A treating agent for treating an exhaust gas containing an inorganic group V compound discharged from a group V compound semiconductor thin film manufacturing step is prepared by mixing anatase type fine particle titanium oxide with basic copper carbonate. Basic copper carbonate is produced by adding a sodium carbonate solution to a solution of copper sulfate or cupric chloride to make the pH neutral to weakly alkaline, washing away the contaminating ions, filtering and drying. However, the basic copper carbonate produced by this method is not very suitable, and in order to achieve a high solid-gas contact efficiency, the average particle diameter by the centrifugal light transmission method is 0.1 mm.
Fine particles having a size of 5 μm or less, preferably 0.3 μm or less are desirable. The method for forming the fine particles having an average particle diameter of 0.5 μm or less may be either fine during the reaction between the copper compound and sodium carbonate or fine by wet or dry pulverization. However, there is a drawback that if the reaction is made fine, the load of the washing step increases.

In order to absorb the heat generated by the reaction between the inorganic group V compound and the copper oxide generated by the thermal decomposition of the basic copper carbonate, the basic copper carbonate must be malachite in order to facilitate the conversion to the copper oxide. The molecular formula known as CuCO ₃ .Cu (O
H) It contains more OH groups than ₂ and its content is at least 1.1 times the theoretical amount, preferably at least 1.2 times the theoretical amount. The content of this OH group controls the pH during the reaction between the copper compound and sodium carbonate, keeps the pH fluctuation during the reaction small, absolutely avoids that the pH changes from neutral to acidic, It can be manufactured while maintaining the temperature at 60 to 70 ° C.

The anatase type fine particle titanium oxide is prepared by neutralizing titanium hydroxide for producing titanium oxide for a pigment by a sulfuric acid method with an alkali agent such as ammonia and washing and removing a sulfate group.
It is manufactured by sintering at a temperature of 300 to 700 ° C. without adding a crystal growth promoter, followed by pulverization. The titanium oxide obtained by this manufacturing method has a crystal system of an anatase type regardless of the temperature, provided that the firing temperature is within this range. The specific surface area and the particle diameter change depending on the firing temperature. As the temperature increases, the specific surface area decreases and the particle diameter increases. The specific surface area of the anatase type fine particle titanium oxide produced at a calcination temperature of 400 to 600 ° C. is 30 to 100.
m ² / g, average particle size 0.3 μm by centrifugal light transmission method
m or less.

The crystal system of the anatase type was selected because
This is because a material having a large specific surface area can be obtained, a large number of pores having a large diameter exist, and an appropriate tackiness is maintained. The treating agent of the present invention is produced by weighing a predetermined amount of basic copper carbonate and anatase type fine particle titanium oxide, adding water, kneading, granulating and drying. The mixing ratio of basic copper carbonate and anatase type fine particle titanium oxide is
The weight ratio is preferably in the range of 60 to 90:10 to 40.

Since the substance itself does not directly participate in the reaction, it is not preferable to increase the ratio of the fine particles of anatase type titanium oxide as a diluent. However, by adding an appropriate amount of anatase-type titanium oxide fine particles, the concentration of basic copper carbonate is uniformly reduced, the calorific value per unit volume is reduced, local heating is avoided, and the specific surface area is large. The air contact area is increased, and the large number of large pores promotes heat dissipation without slowing down the chemical reaction rate and increasing the abatement capacity. There is an advantage that no adhesive other than water is required at the time of molding. If the anatase type fine particle titanium oxide is less than 10%, the above-mentioned gain cannot be obtained,
Even if obtained, it is not enough.

The shape of the molded product of the treating agent produced by weighing at the above ratio, adding water, kneading, granulating and drying is typically a sphere or a column. The size of the compact should be such that the contact area with the exhaust gas is as large as possible when used in a packed tower.However, in order to prevent gas drift in the packed tower, the compact It is said that the body size needs to be smaller than 1/10 of the tower diameter. However, when the size is close to the powder, the pressure loss increases, and there is a problem that dust is generated at the time of handling the filling and taking out of the treating agent, or the molding cost is increased.

In the present invention, drying after molding is important.
If the treatment agent is dried at a temperature exceeding 80 ° C., the effect of suppressing the reaction temperature during exhaust gas treatment cannot be expected because the basic copper carbonate is thermally decomposed into copper oxide. However, drying at a high temperature is not preferable because of the inconvenience that the material shrinks strongly and the structure becomes dense and the solid-gas contact efficiency is reduced. Drying of the treatment agent is performed at low temperature to prevent shrinkage of the treatment agent and maintain the fine pores during molding, the pores after moisture escapes, and the large diameter pores held by the anatase type fine particle titanium oxide. Possible temperature, i.e. 60-
It is preferably carried out at 80 ° C.

If the shape and size of the treatment agent dried after molding is not maintained from the time of filling the cartridge to the time of being used for detoxification and then discharged for refilling, various serious troubles may occur. I do. For example, if powdering occurs during filling or use, the gas flow becomes uneven, or in the worst case it blocks. Therefore, it is required that the treatment agent has a strength necessary to maintain the shape and size of the treatment agent, but the strength can be ensured by mixing an appropriate amount of anatase-type fine titanium oxide particles.

By increasing the strength of the molded article and interposing anatase-type fine particle titanium oxide between the basic copper carbonate, a chemical reaction between the copper oxide generated by the decomposition of the basic copper carbonate and the inorganic group V compound is performed. Since the shrinkage of the volume is reduced, the harm-removing ability of the treatment agent is finally improved.

[0021]

The treatment agent of the present invention removes an inorganic group V compound in an exhaust gas discharged from a III-V compound semiconductor thin film manufacturing process by a chemical reaction with copper oxide generated by decomposition of basic copper carbonate. At the same time, the anatase-type titanium oxide fine particles reduce the amount of heat generated per unit capacity by increasing the contact area with the exhaust gas, promote heat dissipation, and perform local heating with the decomposition heat of basic copper carbonate decomposing into copper oxide. To prevent. In addition, the moldability of the treatment agent is improved by the adhesive force of the anatase-type fine titanium oxide particles, and the shape and size of the treatment agent is maintained from the time the treatment agent is filled into the cartridge to the time it is used and discharged for disposal. Prevents adverse effects due to powdering of the agent.

The concentration of the inorganic group V compound in the exhaust gas used by the treatment agent is not limited, but when the concentration is high, the heat of reaction between the inorganic group V compound and the basic copper carbonate increases, so cooling is necessary. Also occurs.

[0023]

【Example】

Example 1 Basic copper carbonate having an average particle diameter of 0.28 μm, an OH group content of 1.18 times the theoretical value, and a specific surface area of 6
5 m ² / g, anatase-type fine particle titanium oxide having an average particle diameter of 0.18 μm is weighed to a weight ratio of 65:35, mixed well, then added with water and kneaded to obtain a diameter of 1.5 mm × It was formed into a column having a height of 10 mm. This was dried at a temperature of 60 ° C. A mixed gas containing 2.4 vol% of phosphine using hydrogen gas as a carrier gas was introduced into a packed tower in which 445 g of the thus-prepared treating agent was filled in a Pyrex glass tube having a diameter of 45 mm.
It was passed at 9 cm / min.

At this time, the time required until breakthrough was 90 minutes. The maximum temperature of the outer wall was 54 ° C. Further, even when the treating agent was taken out of the glass tube, the size and shape before filling were shown. (Comparative Example 1) Water was added to basic copper carbonate having an average particle diameter of 0.28 µm and an OH group content of 1.18 times the theoretical value and kneaded, and a cylindrical shape having a diameter of 1.5 mm and a height of 10 mm was obtained. Molded. This was dried at a temperature of 60 ° C. A mixed gas containing 2.4 vol% of phosphine using hydrogen gas as a carrier gas was passed at a linear velocity of 39 cm / min through a packed tower in which 288 g of the treatment agent thus produced was filled in a Pyrex glass tube having a diameter of 26 mm.

At this time, the time required until breakthrough was 47 minutes. The maximum temperature of the outer wall was 93 ° C. Also, when the treating agent was taken out of the glass tube, a considerable amount of powder was mixed as compared with before the filling. In addition, for detecting breakthrough in Examples and Comparative Examples, arsine and phosphine detector tubes manufactured by Komei Chemical Co., Ltd. were used.

[0026]

As described above, according to the exhaust gas treating agent of the present invention, the exhaust gas containing the inorganic group V compound discharged in the production process of the group III-V compound semiconductor thin film is reduced in heat generation and temperature. The rise can be suppressed and the treatment can be performed completely. Average particle size of basic copper carbonate is 0.5μ
m or less, high solid-gas contact efficiency can be achieved.

The content of the hydroxyl group in the basic copper carbonate is set to be at least 1.1 times the theoretical amount of the molecular formula CuCO ₃ .Cu (OH) ₂ , so that the copper oxide generated by the thermal decomposition of the basic copper carbonate is reduced. It absorbs heat generated by the reaction with the inorganic group V compound. The average particle size of the anatase-type fine particle titanium oxide is
When the specific surface area is set to 0.3 μm or less and the specific surface area is set to 50 to 80 m ² / g, the reaction with the inorganic group V compound contributes to the uniform dispersion of the basic copper carbonate, and completes the reaction quickly. Since the number of pores having a large diameter is large, the abatement capacity can be increased.

Claims (4)

(57) [Claims] An exhaust gas treating agent for treating an exhaust gas containing an inorganic group V compound discharged from a group III-V compound semiconductor thin film manufacturing process, wherein an anatase type fine particle titanium oxide is mixed with basic copper carbonate. An exhaust gas treating agent characterized by being prepared by: 2. An average particle diameter of the basic copper carbonate is 0.5 μm.
m or less. 3. The method according to claim 1, wherein the content of hydroxyl groups in the basic copper carbonate is at least 1.1 times the theoretical amount of the molecular formula CuCO ₃ .Cu (OH) _2. Exhaust gas treatment agent. 4. An anatase type fine particle titanium oxide having an average particle diameter of 0.3 μm or less and a specific surface area of 50 to 80.
The exhaust gas treating agent according to claim 1, wherein the treating agent is m ² / g.