Reliability of MOSFETs as affected by the interface trap transformation process

An investigation of the long-term time-dependent degradation of the subthreshold characteristics in n-channel and p-channel MOSFETs resulting from Fowler-Nordheim electron injection is discussed. Immediately after the hot-electron injection, degradation in both n- and p-channel transistors due to the hot-electron-induced interface traps is observed. When measured after the hot-electron injection was terminated, however, the subthreshold slope in n-channel transistors exhibits a gradual recovery toward its preinjection level, while that in p-channel transistors continues to degrade with time. This phenomenon can be explained by the interface trap transformation process, which is characterized by a gradual reduction of the hot-electron-induced interface traps above midgap and a gradual increase of the interface traps below midgap.>