1. Technical Field
The present invention relates to a method for treating exhaust gas containing a fluorine-containing interhalogen compound, and a treating agent and a treating apparatus therefor. More specifically, the present invention relates to a method for treating exhaust gas containing a fluorine-containing interhalogen compound, capable of efficiently and safely treating exhaust gas containing a fluorine-containing interhalogen compound gas discharged in the production of a semiconductor or a thin-film transistor liquid crystal display device, and also relates to a treating agent and a treating apparatus for use in the method.
2. Description of the Related Art
The thin-film formation process is common in the fields of producing semiconductors, thin-film transistor liquid crystal display devices and the like. Accompanying this, a dry cleaning gas is used in large amounts in thin-film forming apparatuses. Among these dry cleaning gases, use of fluorine-containing interhalogen compound gas is abruptly growing because it can be used in non-plasma condition and has no global warming effect.
However, the fluorine-containing interhalogen compound gas is highly toxic and dangerous. Therefore, the exhaust gas containing a fluorine-containing interhalogen compound gas must be detoxified and the various treatments described below have been heretofore proposed.
JP-A-3-217217 (the term "JP-A" as used herein means an "unexamined published Japanese patent application") discloses a wet treating method of washing the gas with a mixed aqueous solution of an alkali and a sulfite or bisulfite and a dry treating method of contacting the gas with a solid neutralizer and a solid sulfite or bisulfite. JP-A-3-229618 discloses a dry treating method of contacting the gas with an iron oxide at an ordinary temperature and a dry treating method of contacting the gas with an iron oxide at an ordinary temperature and then contacting it with an alkali agent.
JP-A-4-94723 discloses a dry treating method of contacting the gas with a solid alkali and an adsorbent. JP-A-6-7637 discloses a dry treating method of contacting the gas with a purifying agent comprising a soda lime having supported thereon a copper (II) compound.
Furthermore, a dry treating method of reacting the gas with a mixture of calcium hydroxide and potassium hydroxide to fix it as a solid halide (JP-A-8-215538) and a dry treating method of reacting the gas with a mixture of three compounds of calcium hydroxide, sodium hydroxide and potassium hydroxide to fix it as a solid halide (JP-A-8-215539) are disclosed.
In addition, JP-A-9-234336 discloses a dry treating method of contacting the gas with a purifying agent obtained by adding and adsorbing sodium thiosulfate to a metal oxide mainly comprising copper (II) oxide and manganese (IV) oxide.
However, the above-described wet treating methods as methods for treating a fluorine-containing interhalogen compound gas are disadvantageous in that a wastewater treatment is essentially required after the treatment, which not only makes the apparatus complicated and large-sized but also adds a huge cost for the equipment and maintenance.
Among the dry treating methods, the methods of contacting the gas with a solid alkali such as soda lime (mixture of calcium hydroxide and sodium hydroxide), calcium hydroxide, sodium hydroxide or potassium hydroxide have problems in that the treatment is highly dangerous because the reaction yields a large calorific value, the risk of the solid alkali dissolving or being deliquesced by the water generated in the reaction of a fluorine-containing interhalogen compound with the solid alkali and thereby blocking the treating cylinder having filled therein the processing agent is high, and the treating capability greatly decreases when the solid alkali is dried.
The method of contacting the gas with a sulfite, a bisulfite or an oxide of iron, manganese or copper has a problem that the treating capacity per unit volume of the treating agent is small.
Accordingly, the object of the present invention is to provide a method for treating exhaust gas containing a fluorine-containing interhalogen compound, favored with high treating capacity per the unit volume of the treating agent, high safety with a small calorific value and a low risk of the treating cylinder being blocked due to generation of water, and no reduction in the treating capacity when the treating agent is dried, and to also provide a treating agent and a treating apparatus therefor.