<tex>$hboxCF_4$</tex>Decomposition of Flue Gas From Semiconductor Process Using Inductively Coupled Plasma

Abstract

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.