Chemical vapour deposition of polycrystalline AlN films from AlCl 3–NH 3 mixtures. : Analysis and modelling of transport phenomena

Abstract

AlN deposition experiments from AlCl 3/NH 3 mixtures were carried out in a hot wall chemical vapour deposition (CVD) reactor. The thickness profiles of the deposited films suggested that both reactions and transport of the gaseous species probably play a key role in the deposition process, so a two-dimensional numerical model was developed to analyse mass transfer inside the reactor. From the available information on the AlCl 3/NH 3 or BCl 3/NH 3 chemistry, a chemical scheme was worked out. The homogeneous rate constants were taken from previous works, whereas the analytical expressions of the heterogeneous reaction rates were simply obtained by matching the calculated and experimental deposition rates. Our numerical analysis shows that the heterogeneous reaction of AlCl 3 and NH 3 is an important step in the deposition process, but the homogeneous reaction between AlCl 3 and NH 3 to form AlCl 2NH 2 should also be considered. This analysis also demonstrates that the deposition is controlled by diffusion in some regions inside the reactor. The growth mechanisms of AlN will be further analysed thanks to this modelling, in a second paper.