High-Efficiency PFC Abatement System Utilizing Plasma Decomposition and Ca(OH)$_{2}$ /CaO Immobilization
In order to minimize contributions to global warming, it is important to develop a perfluorocompound (PFC) abatement system that can remove PFCs effectively with low electric power. We have developed a new PFC abatement system consisting mainly of a 2-MHz ICP plasma source and two Ca(OH)2/CaO columns operated under a decompression pressure. Reactive fluorinated compounds including SiF4 are immobilized in the Ca(OH)2/CaO columns without a water scrubber. Stable compounds such as CF4 are excited by the 2-MHz ICP plasma. When the emissions from an Si oxidation film etching process chamber were treated by this abatement system, F2 equivalent removal efficiency was 99.6%, which was about one order of magnitude larger than that of a conventional abatement system. But the CO2 equivalent removal efficiency was calculated to be 91.4% because over 95% of CO2 equivalent emissions were caused by the plasma source power consumption of 2.4 kWh. It means that minimization of the plasma source power consumption, depending on PFC emissions, is a very effective method of minimizing contributions to global warming in a manner similar to improving the PFC removal efficiency.
フッ素固定式パーフルオロ化合物（PFCs）除害システム
In order to minimize contributions to global warming, it is important to develop a Perfluorocompounds (PFCs) abatement system that can remove PFCs effectively with low electric power. We have developed a new PFCs abatement system consisting mainly of a 2 MHz ICP plasma source and two CaO columns operated at low pressure. The CaO agent developed for this system has a specific surface area of 60-80 m2/g and a grain diameter of 2-6 mm, simultaneously. Reactive fluorinated compounds are immobilized in the CaO columns without a water scrubber to prevent the recombination of fluorocarbons. Stable compounds such as CF4 are decomposed by the 2 MHz ICP plasma before introducing in the second CaO column. When the emissions from a fluorocarbon film chemical vapor deposition process chamber were treated by this abatement system, PFCs removal efficiency and CO2 equivalent removal efficiency was 99.96% and 93.5%, respectively.
CF/sub 4/ decomposition of flue gas from semiconductor process using inductively coupled plasma
Flue gases from the semiconductor process, SF/sub 6/, NF/sub 3/, perfluorocarbons (PFCs) such as CF/sub 4/ and C/sub 2/F/sub 6/, and hydrofluorocarbons such as CHF/sub 3/ are being regulated internationally because their gases have extremely large global warming potential in comparison to CO/sub 2/, and they have a long lifetime. PFCs are used for wafer etching and cleanup of chemical vapor deposition chambers. CF/sub 4/ is one of the most stable gases among PFCs and its decomposition is extremely difficult. The purpose of this paper is to develop a PFCs removal system which can be used as the same power supply for both plasma processing and a CF/sub 4/ emission cleanup system in semiconductor manufacturing processes. This achieves higher efficiency and is more economical than conventional systems. CF/sub 4/ decomposition was investigated at low pressure (29/spl sim/53 Pa) using the inductively coupled plasma (ICP) reactor. When the total flow rate was below 0.189 normal liters per minute and O/sub 2/ concentration exceeded the 0.9 stoichiometric ratio, the complete CF/sub 4/ decomposition efficiency was achieved at 1.2 kW. The amount of O/sub 2/ should be a 1/spl sim/1.45 stoichiometric ratio of CF/sub 4/ to achieve good CF/sub 4/ decomposition. The argon enhanced the decomposition of CF/sub 4/. On the other hand, the helium was insignificant. CF/sub 4/ decomposition efficiency decreased in the presence of N/sub 2/. For CF/sub 4/ decomposition, the energy efficiency for CF/sub 4/ decomposition was 21.0 g/kWh at optimal condition using the ICP reactor. From the Fourier Transform Infrared Spectrophotometer analysis, CO and carbonyl fluoride (COF/sub 2/) were produced except for CO/sub 2/. COF/sub 2/ is toxic, however, it hydrolyzes into HF and CO/sub 2/, so it is easy to eliminate COF/sub 2/ using the scrubber which was located downstream of the dry vacuum pump.