A new "multifrequency" charge pumping technique to profile hot-carrier-induced interface-state density in nMOSFET's

Abstract

A new "multifrequency" charge pumping technique is proposed to determine the spatial distribution of interface-state density in nMOSFETs subjected to hot-carrier stress, for situations where negligible charge trapping takes place. It is shown that the increase in charge pumping current with larger gate pulse amplitude is not only due to the increase in charge pumping area, but also due to the increased energy zone of recombination in the band gap. The nonuniformity of interface-state density, spatially near the drain junction and energetically in the band gap scanned by charge pumping also contributes. The resulting uncertainty in the determination of the charge pumping edge using the conventional approach (which neglects the dependence of energy zone of recombination on gate pulse amplitude and assumes spatial uniformity of prestress interface-state density) and hence the error in the extracted post-stress damage profile is pointed out. The new technique uniquely determines the correct charge pumping edge and hence the damage distribution.