CF, CF2, and SiF densities in inductively driven discharges containing C2F6, C4F8, and CHF3

Abstract

Laser induced fluorescence was used to measure the spatially resolved CF, CF2, and SiF radical density in inductively driven discharges containing fluorocarbon gases. Measurements of the spatially resolved CF density were performed in C2F6, and CHF3 containing discharges as functions of inductive power, pressure and bias condition on a silicon substrate. In addition, CF rotational temperatures were calculated, assuming saturated spectra. Measurements of the spatially resolved CF2 and SiF density were performed in C4F8, C2F6, and CHF3 containing discharges as functions of inductive power, pressure and bias condition. SiF rotational temperatures were also estimated. As the induction coil power was increased, the SiF density in the center (r=0 cm) increased while the CF2 density decreased and the CF density slightly decreased. In all cases, the radical density in the center of the glow increased with pressure changes from 5 to 30 mTorr while changes in the bias power had little influence on any of the measured radical densities. The spatial distribution of the CF and SiF density peaked in the center of the discharge. The CF2 density had a local maximum in the center of the plasma with a decreasing density at the edge of the glow. However, the CF2 density outside the glow region was a factor of 2–6 higher than the density inside the glow region, depending on the gas. CF and SiF rotational temperatures were between 450 and 750 K.