Deposition Temperature and Thermal Annealing Effects on the Electrical Characteristics of Atomic Layer Deposited Al2O3 Films on Silicon

Abstract

Atomic layer deposition (ALD) of Al2O3 is of interest for a wide range of micro-nanoelectronic applications, where the electrical properties of the deposited layers can be strongly affected by deposition conditions and post-deposition treatments. In this work, a mercury-probe capacitance-voltage characterization is carried out on Al2O3 films deposited on silicon by ALD at different temperatures and subjected to various thermal treatments in N2 ambient. Effective positive charges located at the semiconductor/dielectric interface are encountered for the films deposited at the lowest temperature (100°C). Positive Vfb shifts are always registered after the different thermal annealing conditions studied; however, the impact of the thermal treatments is found to be different depending on the deposition temperature. A significant negative charges build-up is observed after a 30 min anneal at 450°C, where improved surface passivation properties are achieved. Interestingly, the hysteresis, as well as the Vfb shifts, clearly diminish for higher deposition temperatures or after a thermal anneal. However, the highest temperature treatments (≥800°C) result in significant interface states generation. Finally, exploratory experiments about the stability of the Al2O3 layers under UV-light irradiation (in the 200–300 nm wavelengths range) show that this can be responsible for a significant degradation of their electrical characteristics.