Low temperature boron coatings by microwave plasma assisted chemical vapour deposition

Abstract

Boron coatings are deposited at moderate temperature, equal or lower than 600 °C, from BBr 3H 2 mixtures in a microwave plasma. The deposition rate, the bromine content and the microhardness of the deposits are studied as functions of the deposition parameters. Amorphous boron films are obtained with both high deposition rates, up to 25 μm h −1, and high efficiencies. The bromine content can be lowered to 0.2 at.% and the microhardness varies in the range 1000–3000 kg mm −2 as a function of the temperature, the gaseous composition and the bias voltage applied to the substrate. The bias voltage does not significantly influence the deposition rate, but it can induce some important variations in the bromine content, the morphology and the microhardness. The deposition process is discussed; as a function of the deposition conditions, it appears controlled either by the availability of the inlet reactants or by the convective diffusion of the active intermediate species from their production place to the substrate surface.