Spectroscopic studies of H 2-Ar microwave plasmas containing diborane

Introduction Low pressure molecular microwave plasmas (f = 2.45 GHz) are commonly used for surface processes like thin film depositions. Boron-containing plasma composition provides anticorrosion layers with a considerable high hardness. Processes in the plasma volume connected with the layer formation are only poorly understood. For improving the understanding of important chemical processes in the plasma it is necessary to study the main plasma parameters, which can be obtained by appropriate diagnostic methods. With respect to ground state concentrations of molecular species several non-invasive diagnostic methods have been developed, particularly, emission and absorption spectroscopy and as well as specific laser techniques. Tunable diode laser absorption spectroscopy (TDLAS) was shown to be a useful technique to measure the absolute concentration of the methyl radical and related hydrocarbon species [1]. In the present spectroscopic study, TDLAS has been applied to monitor the absolute concentration of boron containing molecules in their ground state, and optical emission spectroscopy has been used in order to determine the gas temperature.