Dependence of atomic layer-deposited Al2O3 films characteristics on growth temperature and Al precursors of Al(CH3)3 and AlCl3

Abstract

The materials characteristics of Al2O3 films grown on a Si (100) substrate by traveling wave reactor atomic layer deposition were investigated in the growth temperature ranging from 250 to 500 °C. The Al2O3 films grown using Al(CH3)3 trimethylaluminum (TMA) and H2O as precursors were characterized and also compared with the films grown using AlCl3 and H2O. Both samples grown with different precursors revealed identical chemical binding state of oxidized Al and very flat surface morphology. In the study of impurity incorporation, the films grown using TMA showed the C and H count rates of secondary ion mass spectrometry (SIMS) approximately six and 10 times higher than those of the film grown using AlCl3, respectively. For the Al2O3 films grown using TMA, the results showed that the impurity contents and the growth rate of the films decreased and the refractive index increased with the growth temperature. The content of impurities could be also lowered by increasing the N2 purge time after TMA pulse. However, the effect of purge time increase on the impurity incorporation was very small compared to that of growth temperature. The refractive indices were 1.64 and 1.68 at the growth temperatures of 250 and 400 °C, respectively. The rough estimation of H content using refractive indices and SIMS data indicated that the H content decreased from approximately 8.5 to 3.0 at. % as the substrate temperature increased from 250 to 400 °C. The Al2O3 film grown using AlCl3 and H2O at 500 °C, which contained approximately 0.5 at. % Cl, revealed a refractive index of 1.65.