Low-Temperature Atomic Layer Deposition of α-Al₂O₃ Thin Films

Abstract

The atomic layer deposition of Al2O3 films on Si(100) and α-Cr2O3 was studied. The films were grown via AlCl3-H2O, AlCl3-O3, Al(CH3)3-H2O, and Al(CH3)3-O3 processes at 300–750 °C. The films deposited from AlCl3 and H2O at temperatures ≥ 400 °C on α-Cr2O3 contained the corundum phase of alumina (α-Al2O3). The densities and refractive indices of the α-Al2O3 films were close to the corresponding values of single-crystal α-Al2O3 and exceeded markedly those of amorphous Al2O3. The α-Al2O3 phase was also obtained in the films deposited at 450 °C on α-Cr2O3 from AlCl3 and O3 and from Al(CH3)3 and H2O. However, the crystallinity, densities, and refractive indices of the latter films were lower than those of the films deposited at 450 °C on α-Cr2O3 from AlCl3 and H2O. Etching in hot (110 °C) 80% H2SO4 was used to characterize the chemical resistance of the films in aggressive environments. The etching rate of α-Al2O3 deposited at 450–750 °C was more than 1000 times lower than that of predominantly amorphous Al2O3, and also lower than those of the films that were grown on Si(100) at 750 °C and contained γ-Al2O3, δ-Al2O3, and/or θ-Al2O3.