Effects of N2 addition on density and temperature of radicals in 60MHz capacitively coupled c-C4F8 gas plasma

Abstract

Behaviors of electrons and fluorocarbon radicals were investigated in 60MHz capacitively coupled plasma employing mixture gases of c-C4F8, Ar, and N2. Optical emission spectroscopy was applied to measurements of the rotational temperatures of CF radical and N2 molecule, and infrared diode laser absorption spectroscopy was applied to that of the densities of CF and CF2 radicals. The electron density was decreased from 7.3×1010to3.0×1010cm−3, and electron temperature was increased from 3.0to5.1eV with increasing N2 flow rate. The addition of N2 to Ar∕C4F8 plasma decreased the density of CF radical dominantly as compared with CF2 radical. The rotational temperatures of CF radical were estimated from the (1-2) band of BΔ2–XΠ2 electronic transition of CF radicals. It was found that the rotational temperatures of CF radicals were increased with increasing N2 flow rate. The temperatures of radical indicated the different behaviors from the temperatures of N2 molecule. The rotational temperature of CF radical has a good relation with the electron temperature.