Spatially resolved SiF and SiF2 densities in inductively driven discharges containing C2F6 and C4F8

Laser-induced fluorescence was used to measure the spatially resolved SiF and SiF2 radical densities in inductively driven discharges containing fluorocarbon gases. Measurements of the spatially resolved SiF and SiF2 densities were performed in C2F6 and C4F8 discharges as functions of the induction coil power, pressure, and bias power above a silicon surface. The SiF density had a maximum at a radial distance of 2–3 cm from the center of the plasma, and then monotonically decreased towards the edge of the plasma region. While the density was a function of the plasma parameters, the general shape of the SiF spatial distribution was generally independent of the plasma conditions and gas. The SiF2 density had a maximum at a radial distance of approximately 7 cm from the center of the plasma. At this location, the SiF2 plasma-induced optical emission was approximately 10% of the value in the center of the discharge. The SiF2 spatial distribution was dependent on the induction coil power. The location of the peak in the SiF2 density did not depend on the plasma confinement structures or material.