Ultraviolet photo-enhanced atomic layer deposition for improving dielectric properties of low temperature deposited Al2O3

Abstract

Thin films of Al2O3 are deposited using in situ ultraviolet (UV) light enhanced atomic layer deposition (ALD) with trimethylaluminum and H2O and compared to those deposited using traditional thermal ALD at low temperatures of 45 and 80 °C. Coexposing the UV light with the H2O pulse enhanced the growth-per-cycle and refractive index. Metal/insulator/metal devices using the in situ UV enhanced Al2O3 films demonstrated a reduction in leakage current at ±1 MV/cm by nearly an order of magnitude at a deposition temperature of 45 °C as compared to standard thermal ALD films as well as thermal ALD films that received a postdeposition (in vacuo) UV exposure. In addition, capacitance–voltage behavior of UV enhanced Al2O3 showed a dramatic reduction in capacitance–voltage hysteresis. Taken together, these electrical results suggest that in situ UV enhanced ALD of Al2O3 results in a reduced density of electrically active defects that likely arise from incorporated H and potentially other organic impurities left by incomplete surface reactions. This proof-of-concept approach could enable low temperature fabrication of metal/insulator/metal and other devices in temperature-sensitive applications such as flexible electronics.