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Mitsubishi Denki Kabushiki Kaisha

Taiyo Toyo Sanso Co., Ltd.

Masashi Mizuno

Masuo Tada

Norio Yamazaki

Takaaki Fukumoto

Toshiaki Ohmori

Super clean air having therein chemical components&mdash;such as hydrocarbons, organic halogens, acidic gases, basic gases, aldehydes, nitrogen oxides, and H,O (that is, all components other than oxygen, nitrogen, and noble gases&mdash;the types of chemical components differ depending on the source of the air)&mdash;in concentrations no more than 1 ppb and a dew point lower than &minus;40&deg; C., is obtained from the atmosphere by low-temperature adsorption treatment in stages at temperatures ranging from &minus;40&deg; C. to &minus;180&deg; C. Material air collected from the atmosphere is pretreated in a room-temperature adsorption step to remove moisture and carbon dioxide. The pretreated air is then low-temperature adsorption treated by absorbents in a plurality of steps to adsorb the gaseous chemical components, the treatment temperature being lower in each succeeding step. Treatment at &minus;40&deg; C. may remove, for example, HF, SO,, and/or NH,. Treatment at &minus;100&deg; C. may remove, for example, SF,, C,F,, H,S, and/or N,O. Treatment at &minus;150&deg; C. may remove, for example, CF,, NO, CH,, and/or CO. The last treatment step produces super clean air suitable for use in processing semiconductor wafers.

Method for producing super clean air

Super clean air suitable for use in a tunnel-type wafer transport system, etc., is produced efficiently with the specific energy consumption reduced and the yield improved by making good use of part of cooling energy and gas produced in a low temperature separation type nitrogen producing apparatus. Material air 1a collected from the atmosphere is pretreated in a room temperature adsorption tower 7, this pretreated air is adsorption treated at -60.degree. C. in a first low temperature adsorption tower 9, and the treated air 1c is further adsorption treated at -150.degree. C. in a second low temperature adsorption tower 10, thereby producing super clean air 1e containing not higher than 1 ppb of the chemical components other than nitrogen, oxygen and noble gases and having a dew point of not higher than -100.degree. C. The airs 1b and 1c are cooled in heat exchangers 12, 13 and 14 by utilizing cooling energy produced in the low temperature separation type nitrogen producing apparatus, that is, the low temperature gas 3f passed through an expansion turbine 38 from a rectifying tower 37.

Method and apparatus for producing super clean air

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Osaka, Japan

Masashi Mizuno