Toward a better understanding of the nanoscale degradation mechanisms of ultra-thin Si0₂Si films: Investigation of the best experimental conditions with a conductive-atomic force microscope

We report, in this paper, investigations on the experimental conditions to be adopted to improve the reproducibility and the stability of conductive-atomic force microscopy experiments performed on ultra-thin oxide films. In particular, we demonstrate the key role of the water film layer which can disturb the acquisition of ramp voltage stresses and, in fine, lead to an important tip oxidation. Starting from these results, Weibull statistical analyses of stress-induced electrical degradation were carried out under vacuum on SiO₂Si films. We studied the influence of different parameters like the oxide thickness, the substrate doping type and doping level. We also observed important morphological effects, more or less visible, according to the type of tip and the oxide thickness. Those effects can be attributed, on one hand, to different temperature rise at the tipoxide interface and, on the other hand, to different energy dissipated through the oxide film.