Strategic Selection of the Oxygen Source for Low Temperature-Atomic Layer Deposition of Al2O3 Thin Film

Abstract

The influence of two oxygen source types, H2O and O-3, on residual C-related impurities in atomic-layer-deposited (ALD) Al2O3 film is systematically examined. ALD Al2O3 film grown using H2O contains negligible C-related impurities irrespective of growth temperature. However, the C-related impurity in film grown using O-3 exhibits strong dependence on growth temperature; only Al carbonate (Al-CO3) is present in film grown at 300 degrees C, but C-related impurities with lower oxidation states, such as Al-COOH and Al-CHO, appear as the temperature decreases to 150 degrees C. This suggests that the reactivity of O-3 and H2O in the ALD process has a different temperature dependence; from a residual impurity perspective, compared to O-3, H2O is a beneficial oxygen source for low temperature processes. Electrical properties, such as charge trapping and gate leakage current, are also examined. For a growth temperature of 300 degrees C, the film grown using O-3 is slightly superior to the film grown using H2O due to its high film density. However, the film grown using H2O demonstrates better electrical characteristics at low growth temperature, 150 degrees C.