Subthreshold slope and transconductance degradation model in cycled hot electron injection programed/hot hole erased silicon-oxide-nitride-oxide-silicon memories

A physical model is presented for the subthreshold slope and transconductance degradation after program/erase cycling of silicon-oxide- nitride-oxide-silicon memory cells with thick bottom oxide, programed by hot electrons and erased by hot holes. Using a charge-pumping technique, it is shown that the generation of interface states is one of the mechanisms responsible for the degradation of the subthreshold slope and transconductance. In this article, we show the correlation between the increase in the charge pumping current and the decrease in the subthreshold slope and transconductance. Practical solutions are proposed to reduce the influence of the subthreshold slope and transconductance degradation on the overall device performance.