Ultrathin Aluminum Oxide Films Induced by Rapid Thermal Annealing for Effective Silicon Surface Passivation

A novel method of preparing ultrathin aluminum oxide films by rapid thermal annealing (RTA) treatment for effective silicon surface passivation is proposed. The high-temperature RTA processing (750-825 degrees C) for tens of seconds in an oxygen atmosphere completely converts the thermally evaporated aluminum metal nanofilms (1-5 nm) on crystalline silicon to aluminum oxide (Al2O3) films, with a thin SiOx layer formed at the interface between the silicon and the Al2O3. The generated Al2O3 film can provide superior passivation quality for the silicon surface, even better than that obtained by the thermal atomic layer deposition technique. Moreover, the growth kinetics of the Al2O3 passivating film indicates that it is a diffusion-controlled activation process, with an energy barrier of 3.3 eV for aluminum ions diffusing across the metal/oxide interface.