Aluminum oxides ($Al_2O_3$) have been deposited by chemical vapor deposition technique using $AlCl_3$, $CO_2$ and $H_2$ gas mixture onto silicon single crystal. The effects of deposition temperature, partial pressures of reactants, total pressure and total flow rate on the deposition rate and the morphology of the $Al_2O_3$ deposit have been investigated.
It is found that the C.V.D. of $Al_2O_3$ is a thermally activated process and limited by the surface reaction. $Al_2O_3$ deposited at temperatures ranging from 850℃-1000℃ does not show evident crystallity. However, $Al_2O_3$ crystallizes into α-Alumina with heat treatment at 1200℃ in $H_2$ atmosphere after deposition. The deposition rate as a function of $H_2$ partial pressure show a maximum about 25 Torr of $H_2$ partial pressure, which is related to the formation reaction of $H_2O$.
The deposition rate increases as the mole fraction of $AlCl_3$ up to 0.01, and then decreases slightly with higher $Al_2O_3$ mole fractions.
As the total pressure increases, the growth rate also increases, and the morphology of the $Al_2O_3$ deposit becomes porous with $Al_2O_3$ soots formed by the homogeneous reaction.
The morphology of the $Al_2O_3$ deposit is mainly affected by the supersaturation of the reactant gases and growth characteristics.
