A MODEL FOR THE TIME-DEPENDENCE AND BIAS-DEPENDENCE OF P-MOSFET DEGRADATION

Physical properties of both electron trapping and detrapping are ident ified to influence the degradation behavior of p-MOS transistors. Focu sing on electron trapping first, we find as a decisive feature a spati ally growing region of filled traps in the vicinity of the drain. Due to an exponential decrease of the electron injection current as a func tion of distance to the drain, its length grows logarithmically over t ime resulting in a logarithmic time dependence of the degradation. The logarithmic growth of this region is proven by means of charge-pumpin g experiments, whereas the logarithmic time dependence of the degradat ion itself is readily visible in the transistor current. Including ele ctron-detrapping, the model permits a consistent description of both t ime- and bias-dependence of the degradation thereby leading to an impr oved expression for the lifetime of p-MOS transistors.