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-degrees to 1100-degrees-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-degrees-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.