The influence of mechanical stress on the dielectric breakdown field strength of thin SiO2 films

We describe a surface probe technique for measuring the electrical properties of thin films while simultaneously controlling the local mechanical stress. We have used this technique to measure the dielectric breakdown voltage of thin ${\mathrm{SiO}}_{\mathrm{2}}$ films, and we present results which show that there exists a correlation between the dielectric breakdown strength and the mechanical stress applied to the oxide. We propose a model, in which the mechanical strength of the material provides the criterion for breakdown, which accounts well for this behavior. Apart from the possible importance in the breakdown mechanism, the results suggest that residual stresses in insulating films may influence their effectiveness as dielectrics.