Is there a limit for the passivation of Si surfaces during anodic oxidation in acidic NH4F solutions?

The interface state densities of wet anodic oxide layers on Si are normally very high and, therefore, there is need for special post-treatments. Repetitive oxidation/hydrogenation cycles in the current oscillating regime lead to improved passivation of the SiO2/Si interface. The atomic force microscopy (AFM) images reveal the formation of macroscopically rough surfaces (holes with a diameter of at least 100 nm and a depth of up to 10 nm). This kind of surface structure is more favourable to decrease the strain induced by the Si-O-Si bond angle mismatch. This peculiarity of Si surfaces conditioning in acidic NH4F solutions leads to a reduction of the defect concentration at the SiO2/Si interface without further processing. (C) 2000 Elsevier Science Ltd. All rights reserved.