6-T cell circuit dependent GOX SBD model for accurate prediction of observed vccmin test voltage dependency

The effect of oxide soft breakdown (SBD) on the reliability of a 6-T cache cell has been examined and a circuit based gate oxide (GOX) reliability model has been developed. The results show that a model that combines the circuit topology, PMOS bias temperature (PMOS BT) effect, and a SBD time dependent leakage model allows for accurate prediction of the observed vccmin test voltage dependence. Through simulation it was determined that PMOS BT plays a significant role in aggravating SBD effects on stability. Examples are shown of cell stability using a simplified circuit SBD model including varying amounts of PMOS BT degradation on the two PMOS pull up devices, a SBD time evolution model for NMOS devices is explained, and finally a comprehensive model combining all of these effects is presented along with initial data verifying model trends.