Breakdown kinetics at nanometer scale of innovative MOS devices by conductive atomic force microscopy

The breakdown (BD) kinetics of dielectrics represent a crucial issue for the reliability of microelectronics devices. In this paper, we report on an innovative and practical approach based on Conductive Atomic Force Microscopy (C-AFM) for the determination of the BD kinetics on a bare insulator surface. This technique has been applied to Pr2O3 films grown by Metal-Organic Chemical Vapour Deposition (MOCVD) on Si(0 0 1) and to thermally grown SiO2 on 4H–SiC substrates. C-AFM clearly visualizes single breakdown spots under constant voltage stresses. The stress time on the C-AFM tip was varied from 1 × 10−3 to 1 × 10−1 s. The density of BD spots, upon increasing the stress time, exhibits in both cases an exponential trend. The Weibull slope of the dielectric BD statistics has been determined by direct measurements at nanometer scale on different dielectrics having different physical thicknesses. The comparison of the Weibull slopes obtained for different dielectric thicknesses with literature data points out intrinsic and extrinsic BD events in the SiO2/SiC system and Pr2O3 based layers, respectively. In the case of the SiO2/SiC system, BD kinetics have been demonstrated to follow the percolation model, while the role of extrinsic phenomena in the BD of Pr2O3 films has been proved.