EFFECT OF PARTIAL-PRESSURE OF THE REACTANT GAS ON THE CHEMICAL VAPOR-DEPOSITION OF AL2O3

Abstract

Films of Al2O3 were deposited onto TiN-coated cemented carbide substrates by a chemical vapour deposition technique using AlCl3, CO2 and H2 gases. The effects of the deposition temperature and the partial pressures of the reactants on the final structure of the Al2O3 film were investigated, especially the effect of the supersaturations of the reactants (H2O and AlCl3) on the final structure of the Al2O3 film. The supersaturations of the reactants are calculated assuming chemical equilibria. It is found that the deposition rate of Al2O3 is limited by both the AlCl3 concentration and the [H2]/[CO2] ratio, but the crystal size of Al2O3 film decreases with increasing H2O supersaturation. The supersaturation of AlCl3, however, seems not to affect the crystal size of Al2O3 film under our experimental conditions. It is also found that the crystallographic structure of the Al2O3 film changes from random orientation to (1014)-preferred orientation with increasing deposition temperature.