A model relating wearout induced physical changes in thin oxides to the statistical description of breakdown

A model that relates the physical wearout caused during high voltage or high current stressing of thin oxides to the measured statistical time-dependent dielectric breakdown (TDDB) distributions is discussed. Wearout is described in terms of changes that occurred in the oxide prior to breakdown. Traps are generated within the oxide during wearout and breakdown occurs locally when the local density of traps exceeds a critical value. The model is used to quantify several effects observed during TDDB measurements. The area dependence of breakdown distributions, the differences in the breakdown distributions of constant current stresses and constant voltage stresses and the multimodal distributions often observed are simulated using physically measured quantities and realistic assumptions about the trap distributions inside the oxides. Several TDDB distributions measured by others are fitted using the model developed.<>