Ozone-based batch atomic layer deposited Al₂O₃ for effective surface passivation

In this paper we compare water and ozone as oxidants in the Al₂O₃ ALD reaction in terms of surface passivation quality. The experiments show that O₃ produces a high negative charge density up to 7·10¹² cm^-2 even in as-deposited film, which is different from water based Al₂O₃ that requires a separate annealing step to activate the negative charge. In general, the ozone process produces lower interface defect density (Dit) and higher negative charge density, which contributes to the higher lifetime value than corresponding water process. Most importantly, ozone-based Al₂O₃ shows much better firing stability than water-based Al₂O₃. Ozone concentration is also shown to play a role in the surface passivation quality. Finally, we found out that inserting a water pulse after the ozone pulse can lower the Dit further resulting in even higher lifetime.