Feasibility of the electrical characterization of single SiO2 breakdown spots using C-AFM

Due to the progressive scaling down of MOS devices, new methods are required to study the failure mechanisms of the gate oxide in a nanometer range. In this work, an atomic force microscope equipped with a conductive tip and a sensitive preamplifier has been used to study the electrical properties and degradation dynamics of single breakdown spots of 3–6 nm SiO₂ films on a nanometer scale. With this purpose, voltage ramps over areas of 30–50 nm² (of the order of the breakdown spot area) have been repeatedly applied to induce the degradation of the SiO₂ films. Similar results to those observed with conventional tests (such as the switching between two states of well-defined conductivity) have been measured with this technique. As a conclusion, our results point out the conductive atomic force microscope as a tool for the analysis of the electrical properties and degradation of single breakdown spots.