Electrode length effect on the abatement efficiency of N2O in low-pressure plasma reactor

Abstract

Regulations on the emission of greenhouse gases have been made stricter worldwide for mitigating global warming. The semiconductor and display industries emit significant amounts of greenhouse gases, such as N2O and F-gases. We investigated the electrode length effect on the abatement characteristics of N2O in a low-pressure plasma reactor. N2O is extensively used in SiO2 thin film depositions, SiCl2 + 2N2O → SiO2(s) + 2N2 + Cl2, and its global warming potential (GWP) is 310 (GWP of CO2 = 1). The destruction and removal efficiency (DRE) of N2O was evaluated by using Fourier transform infrared (FTIR) spectroscopy. The DRE of N2O was reduced with increasing the N2O flow rate or decreasing the pressure. A larger electrode length yields a higher DRE, especially for higher N2O flow rate and lower pressure conditions. For understanding this phenomenon, the discharge characteristics were analyzed by using optical emission spectroscopy (OES). Molecular emissions from N2(C-B) and N2+(B-X) bands were measured together with atomic emissions from O I (777 and 844 nm) lines, by varying the electrode length. The reason for a larger electrode length to achieve a higher DRE was explained in terms of the plasma property and gas residence time.