CF4 decomposition of flue gas from semiconductor process using inductively coupled plasma

Flue gases from the semiconductor process, SF₆, NF₃, perfluorocarbons (PFCs) such as CF₄ and C₂F₆, and hydrofluorocarbons such as CHF₃ are being regulated internationally because their gases have extremely large global warming potential in comparison to CO₂, and they have a long lifetime. PFCs are used for wafer etching and cleanup of chemical vapor deposition chambers. CF₄ 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 CF₄ emission cleanup system in semiconductor manufacturing processes. This achieves higher efficiency and is more economical than conventional systems. CF₄ decomposition was investigated at low pressure (29∼53 Pa) using the inductively coupled plasma (ICP) reactor. When the total flow rate was below 0.189 normal liters per minute and O₂ concentration exceeded the 0.9 stoichiometric ratio, the complete CF₄ decomposition efficiency was achieved at 1.2 kW. The amount of O₂ should be a 1∼1.45 stoichiometric ratio of CF₄ to achieve good CF₄ decomposition. The argon enhanced the decomposition of CF₄. On the other hand, the helium was insignificant. CF₄ decomposition efficiency decreased in the presence of N₂. For CF₄ decomposition, the energy efficiency for CF₄ decomposition was 21.0 g/kWh at optimal condition using the ICP reactor. From the Fourier Transform Infrared Spectrophotometer analysis, CO and carbonyl fluoride (COF₂) were produced except for CO₂. COF₂ is toxic, however, it hydrolyzes into HF and CO₂, so it is easy to eliminate COF₂ using the scrubber which was located downstream of the dry vacuum pump.