Effect of current levels on memory behaviour of MNOS structures — Limits of computer simulation

MNOS memory hysteresis and memory window are simulated by calculation of tunneling probability via the potential barrier to the nitride conductance or valence band, or to Si nanocrystals embedded in the dielectric layers. The effect of the oxide and nitride current levels are studied. The memory hysteresis width depends strongly on the oxide current level. If the oxide current is close to the nitride current, the flat-band voltage shift is low. If the oxide current is lower than the nitride current, the hysteresis curve changes its direction. The nitride current level affects the hysteresis height only due to charge loss via the nitride layer. At very high oxide currents the memory behaviour collapses, but it is obtained by the simulation of memory hysteresis only, it does not appear in the simulation of memory window.