Spatial dependence of the optical emission intensities from CF4+O2 plasmas

Optical emission intensities from CF4+O2 plasmas are measured at various positions in a rf parallel plate reactor. Since the emission intensities are measured at two different positions between the anode and the cathode electrodes simultaneously, the intensity at either position can be used as a reference to check fluctuations of plasma conditions. Though the raw measured emission intensities depend strongly on the position, the emission intensities normalized to Ar emission vary less than 15%. Although the generation rates of plasma species may depend on the position, the spatial distributions of the plasma species densities are nearly uniform because of diffusion. However, effects of the generation rate and/or the gas flow must also be considered when the spatial dependencies of the plasma species are examined in detail.