A model for the time- and bias-dependence of p-MOSFET degradation

Physical properties of both electron trapping and detrapping are identified to influence the degradation behavior of p-MOS transistors. Focusing on electron trapping first, we find as a decisive feature a spatially growing region of filled traps in the vicinity of the drain. Due to an exponential decrease of the electron injection current as a function of distance to the drain, its length grows logarithmically over time resulting in a logarithmic time dependence of the degradation. The logarithmic growth of this region is proven by means of charge-pumping experiments, whereas the logarithmic time dependence of the degradation itself is readily visible in the transistor current. Including electron-detrapping, the model permits a consistent description of both time- and bias-dependence of the degradation thereby leading to an improved expression for the lifetime of p-MOS transistors.<
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