Dry-Type off-Gas Treatment Technology of Exhaust Gases From the Semiconductor Industry for Fluorine Recycling

Wednesday, October 19, 2011: 8:50 AM
101 G (Minneapolis Convention Center)
Shinji Yasui1, Syunpei Yamaji2, Tadashi Shojo3, Goichi Inoue3, Kunihiko Koike3, Akihiro Takeuchi4 and Yoshio Iwasa4, (1)Tsukuri College, Nagoya Institute of Technology, Nagoya, Japan, (2)Department of Computer SCIENCE and Engineering, Nagoya Institute of Technology, Nagoya, Japan, (3)Shiga Technology Center, Iwatani International Corporation, Shiga, Japan, (4)Energy Application Research & Development Center, Chubu Electric Power Co., inc., Nagoya, Japan

A dry-type off-gas treatment process for recycling fluorine from perfluoro compounds present in off-gases from the semiconductor industry has been developed. This treatment process consists of an electric thermal furnace for the decomposition of perfluoro compounds, a filter, and a fixation furnace for the adsorption of fluorine compounds. In the thermal decomposition furnace, the NF3 and SiH4 released from the chemical vapor deposition (CVD)chamber during the etching or cleaning processes are decomposed to HF, SO2, and SiF4 in the presence of water vapor. Next, the filter recovers SiO2 powder from the exhaust gas released from the decomposition furnace. Finally, in the fixation furnace, two types of granular solid adsorbents—calcium carbonate and a sodium compound—adsorb the HF and SiF4 present in the off-gas, and the gases are recovered as calcium fluoride and sodium fluorosilicate, respectively, for recycling. This paper describes the fluorine compound adsorption properties of both the solid adsorbents—calcium carbonate and the sodium compound—for the optimal design of the fixation furnace. An analysis of the gas-solid reaction rate was performed using the experimental results of the breakthrough curve for each solid adsorbent, and the reaction rate constants and adsorption capacity were obtained for achieving an optimal process design.

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