Kinetic and Thermodynamic Analyses of Chemical Vapor Deposition of Aluminum Nitride

AIN coatings were prepared by chemical vapor deposition from the AlCl₃—NH₃—Ar reagent system using an impinging jet reactor in the temperature range of 700° to 1100°C. A mass transfer model and thermodynamic calculations were used to analyze the deposition data. The AIN-CVD process could be approximated by calculating mass transfer—thermodynamic limits at low AlCl₃ concentrations. The AIN deposition rate decreased drastically with increasing temperature above 1000°C in agreement with thermodynamic predictions. At high AlCl₃ concentrations, a surface kinetic mechanism involving AlCl₃ adsorbed on the deposition surface appeared to be the rate-limiting step. The AIN deposition rate decreased on increasing the AlCl₃ concentration or total pressure. The crystalline structure of AIN was strongly influenced by the processing parameters. The AIN coatings became highly crystalline and preferentially oriented with an increase in the AlCl₃ concentration or pressure.