C-AFM and KPFM Characterization of poly-Si/SiOx/c-Si Passivated Contact Structure

Poly-Si/SiOx/c-Si structures were characterized using conductive AFM (C-AFM) and Kelvin Probe Force Microscopy (KPFM) techniques with the objective to provide a better understanding of the structure, and notably the presence of nanoholes in the oxide. The observed samples include highly doped poly-Si layers annealed at different temperatures (700, 800 and 900 °C) and also intrinsic poly-Si layers. The latter layers have been in particular implemented to facilitate C-AFM and KPFM correlative analysis on the same scan areas. It is found that the C-AFM technique is not conclusive due to the high doping and surface morphology of the poly-Si layer. On the other hand KPFM allows to observe local surface potential drops that may be correlated to holes in the oxide. Correlative microscopy measurements applied on intrinsic poly-Si allowed to evidence links between C-AFM and KPFM observations, however surface conduction effects on c-AFM still remain.