Properties of aluminium oxide films prepared by plasma-enhanced metal-organic chemical vapour deposition

Abstract

Aluminium oxide films were deposited on silicon substrates at low temperatures (150–300 °C) by plasma-enhanced chemical vapour deposition using trimethylaluminium, N 2O and helium gases. The film properties including chemical composition, depth profile, microstructure, refractive index and step coverage were investigated, and the dependence of the film properties and deposition rate on the deposition temperature were also studied. The deposition rates of aluminium oxide films deposited at 150 and 170 °C are very high, reaching 320–400 Å min −1. On the contrary, above 200 °C the deposition rates are constant at 160 Å min −1. The film deposited at 150 °C has an amorphous structure and those above 250 °C have an extremely fine γ-alumina crystalline structure. Hydrogen is the only impurity detected in the aluminium oxide film and its concentration increases as the deposition temperature decreases. The film deposited at 250 °C exhibits a very smooth surface and fairly conformal step coverage. The temperature dependence of the deposition rate and hydrogen content is explained by the change in adsorption type and desorption rate of reactants with temperature.