Simulation of Statistical Aspects of Charge Trapping and Related Degradation in Bulk MOSFETs in the Presence of Random Discrete Dopants

The distribution of fractional current change and threshold voltage shift in an ensemble of realistic 35 nm bulk negative-channel metal-oxide-semiconductor field-effect transistors caused by charge trapping on stress-generated defect states at the Si/SiO₂ interface is studied using 3-D statistical ¿atomistic¿ simulations. The simulations take into account the underlying random discrete dopant distribution in the transistors, which in conjunction with strategically positioned traps could result in rare but dramatic changes in the transistor characteristics. The evolution of threshold voltage distribution as a result of accumulation of trapped charges in the devices due to progressive negative bias temperature instability, positive bias temperature instability, or hot electron degradation is simulated and compared with simple analytical model predictions and recently published experimental measurements to demonstrate the necessity to consider statistical variability in realistic reliability simulations. The magnitude of the degradation in devices of different geometries is also investigated where minimal correlation is found.