Kiel 2004 – wissenschaftliches Programm
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P: Plasmaphysik
P 3: Postersitzung: Niedertemperaturplasmen Plasmatechnologie I, Diagnostische Methoden I
P 3.5: Poster
Montag, 8. März 2004, 17:45–19:30, Foyer
Investigation of the reaction kinetics in methane discharges by means of tunable diode laser absorption spectroscopy — •I. Möller, A. Serdioutchenko, and H. Soltwisch — Institut für Experimentalphysik, Ruhr-Universität Bochum, 44780 Bochum, Germany
Low-temperature rf discharges with CH4 as source gas have been used for the deposition of films for a long time. Nevertheless, the interdependence of the production and consumption channels of the various molecular species and their dependence on the external parameters (like power or flow rate) and the internal parameter (like the electron energy distribution function (EEDF)) are not yet understood.
In this work two different plasma reactors (a capacitively and an inductively coupled cell) have been used to increase the range of external and internal parameters. An absorption spectrometer with tunable diode lasers has been set up for the investigation of molecular densities. The source gas (CH4), one intermediate radical (CH3) and two stable end products (C2H6 and C2H2) have been measured. Their dependence on the input power can be explained by simple semi-empirical expressions, which allow to identify the main production and loss channels. The influence of the flow rate on the species concentrations and the plasma on and off time scales have been studied. In addition, a simple chemical model has been established, which uses the EEDF as input parameter. By comparing the calculated chemical composition with the measured molecular densities a reasonable EEDF can be predicted.