Position-Dependent Nanoscale Breakdown Characteristics of Thin Silicon Dioxide Film Subjected to Mechanical Strain

This paper investigates the nanoscale breakdown characteristics of thin silicon dioxide (SiO₂) films subjected to mechanical strain. A uniaxial compressive strain or a tensile strain was applied to the oxide samples using a homemade bending tool followed by the application of a ramped voltage stress (RVS) or a constant voltage stress to the oxide samples by means of a conductive atomic force microscope tip. The nanoscale current versus voltage (I-V) characteristics and the cumulative failure distributions of the oxide breakdown voltage for the RVS as well as the nanoscale current versus time (I-t) characteristics and cumulative failure distributions of time to breakdown at various surface positions along the strain axis were determined. The nanoscale breakdown characteristics of the strained oxide samples after Co-60 γ-ray irradiation were also investigated. It was found that the central region of both the preand postirradiated strained samples always exhibited a higher oxide leakage current, a lower oxide breakdown voltage, and a shorter time to breakdown than the side regions, regardless if they were under compressive or tensile strain. Our experimental results also showed that interfacial strain release as well as the nanoscale bias-annealing effect increased the Weibull slope β and 63%T_BR in the center region of the postirradiated strained oxide samples, compared to the preirradiated ones.