Abstract: A dust removing apparatus equipped with a back washing mechanism and a dust removing method for removing solid silica fine powder contained in a gas discharged from a semiconductor producing step of a single-wafer processing atmospheric pressure CVD apparatus without causing problems caused by the increase of a pressure loss and by a pressure fluctuation, wherein filter elements each having a ratio of a surface area of a primary side of a filter membrane to an apparent external surface area of the filter element of from 1 to 5 is used, gas jetting nozzle(s) for back washing is formed in the secondary side of the filter element, back washing is not carried out during filtration in the filter element and at or after changing the processing of a wafer in the CVD apparatus, back washing is carried out to blow down the silica fine powder accumulated on the primary side of the filter membrane.

Abstract: A cleaning agent for removing acidic gases which are harmful materials from a harmful gas containing such acidic gases, and a cleaning method using the cleaning agent are disclosed. The cleaning agent comprises a molded product of a composition comprising strontium hydroxide and an iron oxide, and the harmful gas is passed through a cleaning column packed with the cleaning agent to contact the harmful gas with the cleaning agent, thereby removing the acidic gases from the harmful gas.

Abstract: There is disclosed a process for cleaning a harmful gas which comprises bringing a gas containing a basic gas as a harmful component such as ammonia and amines into contact with a cleaning agent comprising a cupric salt supported on an inorganic carrier composed of an metallic oxide such as silica and alumina or a metallic oxide mixture of cupric oxide and manganese dioxide to remove the harmful component from the gas containing a basic gas.According to the above process, it is made possible to effectively remove a basic gas such as ammonia and trimethylamine contained in the exhaust gas from semiconductor production process; and a harmful basic gas contained in dilution gas such as air or nitrogen which dilutes the harmful gas suddenly leaked in emergency from a gas bomb filled inside with the harmful gas. Moreover, the process enables to prevent the occurrence of fire even in the coexistence of other gas such as silane, while maintaining excellent effect on the removal of the harmful gas.

Abstract: There is disclosed a process for cleaning a harmful gas which comprises bringing a harmful gaseous halogenide 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 into contact with a cleaning agent comprising zinc oxide, aluminum oxide and an alkali compound to remove the above halogenide. The above process is extremely effective for promptly and efficiently removing the above gaseous halogenide that is contained in the gas discharged from semiconductor manufacturing process.

Abstract: A process for cleaning a harmful gas which includes contacting a gas containing as a harmful component an alkoxide compound of the formula M(OR).sub.x, wherein M is a metallic element, OR is an alkoxy group and x is the valency of the metal, such as trimethylphosphorous, with a cleaning agent, which is an alkali metal compound such as potassium hydroxide, sodium hydroxide and potassium oxide, supported on a metallic oxide composition comprising cupric oxide and manganese dioxide, wherein the total amount of the cupric oxide and the manganese dioxide is at least 60% by weight based on the total amount of the metallic oxide, to remove the harmful component from the harmful gas. The process effectively and safely removes harmful components in gases exhausted from semiconductor manufacturing processes.

Abstract: There is disclosed a process for cleaning a gas containing a nitrogen fluoride especially nitrogen trifluoride as the harmful component which comprises bringing the gas into contact with a cleaning agent comprising zirconium or a zirconium-based alloy such as Zr-Fe, Zr-Cu, Zr-Ni, Zr-Al, Zr-Mg, Zr-Ca, Zr-Zn, Zr-La and Zr-Ce to remove the harmful component at 100.degree. to 800.degree. C., especially 150.degree. to 500.degree. C. The process is capable of efficiently removing nitrogen fluoride, especially nitrogen trifluoride at a relatively low temperature without generating a harmful byproduct such as nitrogen oxide, and thus exhibits excellent effect on the cleaning of exhaust gas from semiconductor manufacturing process, etc.

Abstract: There is disclosed a process for cleaning a harmful gas which comprises bringing a harmful gaseous halogenide 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 into contact with a cleaning agent comprising zinc oxide, aluminum oxide and an alkali compound to remove the above halogenide. The above process is extremely effective for promptly and efficiently removing the above gaseous halogenide that is contained in the gas discharged from semiconductor manufacturing process or leaked suddenly from a gas bomb in an emergency.