NMOS predope enhanced off-state leakage current

Parasitic transistors, which cause a subthreshold kink at high substrate bias, are a common phenomenon for STI (shallow trench isolation) technology. The normal cause of this phenomenon is gate oxide thinning at the edge of the STI interface. Due to the much lower threshold voltage for these STI edge parasitic transistors as compared to the main transistor, the off-state leakage current (I_off) may become higher than that in the absence of STI gate oxide thinning. In this paper, an NMOS predope enhanced I_off outlier that is related to the subthreshold kink was observed. The influence of Npoly predope implant dose and energy was studied and discussed.