Stored charge properties of anodic aluminium oxide on silicon substrate

Anodic aluminium oxide (AAO) has been demonstrated to electronically passivate silicon surfaces, with one of the important contributors to the passivation being the electric field created by the stored charges in the AAO. This paper reports the stored charge properties of AAO calculated from MOS (Metal-Oxide-Semiconductor) capacitance-voltage (C-V) measurements and contactless corona C-V measurements. Results from both methods suggested that AAO stores a high density of positive charges, which are influenced by the properties of the intervening dielectric layers. Test structures were fired in an industrial belt furnace and the impact of firing on fixed charge density, interface state density and passivation were ascertained.