TRACE RARE-GASES OPTICAL-EMISSION SPECTROSCOPY FOR DETERMINATION OF ELECTRON TEMPERATURES AND SPECIES CONCENTRATIONS IN CHLORINE-CONTAININGPLASMAS

Trace rare gas optical emission spectroscopy has been used to obtain e lectron temperatures (T-e) and percent dissociation of Cl-2 in chlorin e-containing, high-density inductively (transformer) coupled plasmas. In this method, a small amount of an equal mixture of the rare gases i s added to the plasma and emission spectra that include lines from the rare,oases are recorded. Modeling of the dependence of the rare gas e mission intensities on T-e allows T-e to be derived from the best matc h between the observed and computed intensities. T-e in Cl-2 plasmas i ncreases from 1.7 eV at 20 mTorr to 3.4 eV at 0.5 mTorr. These values are 1.3 to 1.8 times lower than those recorded with a Langmuir probe. This discrepancy is due at least in part to artifacts associated with using a single Langmuir probe in a reactor with semiinsulating walls. Absolute percent dissociations of Cl-2 were determined by monitoring t he intensity of an emission band of Cl-2, normalized to emission from Ar and Xe. Cl-2 percent dissociation increased with power and decrease d with pressure. At 1.0 mTorr, Cl-2 is about 85% dissociated at a powe r density of 0.1 W/cm(3) and 95% dissociated at 0.3 W/cm(3) in a Cl-2 plasma. Addition of BCl3 to Cl-2 increases the dissociation of Cl-2.