Study of interface states and oxide quality to avoid contrast reversal in scanning capacitance microscopy

We demonstrate that the contrast reversal effect in scanning capacitance microscopy (SCM) is related to the Si/SiO2 interface microroughness. The surface roughness has been associated with the concentration of states at the Si/SiO2 interface and a monotonic behavior of the SCM imaging is preferentially observed for a smooth surface and consequently a low state concentration. Changes in the oxide quality have also been found to strongly influence the measurements. A criterion based on the hysteresis measurements from forward and reverse dC/dV-V curves is discussed to better evaluate the oxide quality and to obtain reproducible SCM data.