Plasma Deposition of Inorganic Thin Films

Abstract

The possible use of electrical discharges for the preparation of exotic materials has intrigued chemists for nearly as long as the properties of the discharges themselves have been studied by physicists and engineers (1). The use of discharges in chemical reactions now falls under the general subject heading of plasma chemistry. Applications range from extractive metallurgy (2) to investigations of the origins of life itself (3). Polymerization of organic monomers with electric discharges has had periodic popular appeal (4) but has failed to mature into any widespread application. Free radical reactions, which are readily prepared in glow discharges, have been extensively investigated, and their properties are reviewed elsewhere (5). A widespread application of plasma methods for the deposition of dielectrics was developed with the discovery of RF sputtering (6). With the possible exception of reactive RF sputtering, however, this is considered a physical deposition process and is nbt covered in this article. The subject of this review is plasma-enhanced deposition, sometimes referred to as reactive plasma deposition (RPD), of primarily inorganic nonconducting thin films. In this process, gases that normally do not react or decompose at the applied temperature are introduced at moderate pressure (0.1-10.0 torr) into a reaction chamber, and an electric discharge is initiated. The energy coupled into the gas is chosen, along with the other parameters of the system, to produce deposition on exposed surfaces. The development of this process is primarily motivated by the electronics industry, where thin dielectric films are widely used in the manufacture of semiconductor devices. Reactors capable of handling production quantities of material with well-controlled and reproducible results have been developed.