Stress Dependent Activation Energy

Abstract

Due to recent reports of stress-dependent activation energy, a generalized Eyring model has been developed in order to better understand thermally activated failure mechanisms. The model predicts a stress-dependent activation energy provided two necessary requirements are satisfied: (1) the applied stress must be the same order of magnitude as the strength of the material and (2) the stress acceleration parameter ¿ must be a function of the temperature. This model has been successfully applied to diverse failure mechanisms such as: dielectric breakdown under electric-field stress, metal failure under mechanical stress, and electromigration failure under current density stress. Application of model to the specific case of electromigration suggests that the current density exponent N for failure is not a unique value but increases with current density from N=1 at J ¿ 1 × 105 A/cm2 to N¿2 at J ¿ 1 × 106 A/cm2.