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.