Hot-hole-induced negative oxide charges in n-MOSFETs

We investigate the generation of electron traps by hole injection during hot-carrier stressing of n-MOSFETs. These generated electron traps are filled by an electron injection following the primary hole stress. The effect is proven and quantified by monitoring the detrapping kinetics in the multiplication factor and the charge pumping current. The traps are located in the oxide within the first few nanometers to the interface. An interaction of those traps with interface states is found in that charged electron traps inhibit charging or uncharging of interface states. The kinetics of hot-carrier-induced fixed negative charges in n- and p-channel MOSFET's are compared showing significant differences in the properties of the two species of traps. Hole-induced electron traps are located much closer to the interface and their energetic level is deeper. Finally, a method is presented that allows the quantification of the effect for reliability purposes. We conclude that under digital and analog operation conditions in which hole effects cannot completely be ruled out, this effect has to be considered.<
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