Development and Validation of a Mathematical Model for the Chemical Vapor Deposition of Alumina from Mixtures of Aluminum Trichloride, Carbon Dioxide, and Hydrogen

Abstract

Detailed homogeneous and heterogeneous chemistry models are formulated for the chemical vapor deposition (CVD) of alumina from mixtures of aluminum trichloride, hydrogen, and carbon dioxide. Since formation of the species that are required for the incorporation of oxygen atoms in the film (primarily and OH) takes place through the pathways of the water-gas-shift reaction, a complete kinetic model for this process is incorporated as a submodel in the homogeneous chemistry model. Information obtained from the analysis of the thermodynamic equilibrium in the gas phase of the reacting mixture and from past experimental and theoretical studies is employed to determine which elementary reaction steps play an important role in the overall deposition process. The kinetic model is introduced into the transport and reaction model of a tubular, hot-wall CVD reactor, and it is employed to obtain results on the effects of the operating conditions on the variation of the gas-phase composition, deposition rate, and surface species coverages with residence time, under conditions typically encountered in aluminum oxide chemical vapor deposition. Experimental data obtained in a tubular, hot-wall CVD reactor in our laboratory are used to validate the predictions of the overall model. The model is found to be capable of reproducing successfully the experimental data and the various behavior patterns observed in the experiments, such as the occurrence of a maximum in the variation of the deposition rate with parameters that affect strongly the residence time of the mixture in the reactor. © 2002 The Electrochemical Society. All rights reserved.