Chemistry studies of low-pressure argon discharges: Experiments and simulation

Abstract

This chapter presents the chemistry studies of low-pressure electrical discharges generated with argon gas. This noble gas is widely used in gas-discharge lamps, as sputtering gas for deposition and/or etching processes, arc welding, among others. Especially, in the semiconductor industry, this gas is present in most of the processing steps of a chip or a micro device. The magnetron sputtering reactor, designed for the deposition of thin films, and the reactive ion etching reactor, designed for etching process of materials at micro/nano scale level are among the most common equipment that use argon-based plasma environment. Moreover, microplasma reactors can currently generate plasmas at pressures of the order of tens of Torr. In order to tune or better understand these plasmas, it is necessary to investigate the chemistry occurring in their generation and during the self-sustained discharge. Experimental diagnostic tools, such as Langmuir probe and optical emission spectroscopy, are used to determine plasma/gas parameters namely electron density, electron temperature, argon ion density, metastable species, gas temperature, etc. In argon discharges, several excited and metastable species are observed, and they affect the physics and chemistry of the medium due to occurrence of multistep and Penning ionization processes. These ionization modes appear commonly when discharge parameters such as pressure or power are increased, but are strongly dependent on the concentration and distribution of the metastable species as well as reactor geometry. Thus, simulation tools are essential to complement the experimental data and explain the discharge mechanisms. In this work, some primarily results of plasma simulations with collisional-radiative model are presented. Moreover, a revised set of collisional-radiative reactions are presented and discussed. Finally, for the case of magnetron sputtering plasma, a brief discussion about the influence of argon gas incorporation in the properties of the grown thin films by this technique is presented. © 2013 by Nova Science Publishers, Inc. All rights reserved.