Influence of Device Parameters on Memory Performance of MNOS Structure

The influence of various device parameters on the characteristics of MNOS (metal-nitride-oxide-silicon) memory devices has been examined. Three types of charge storage are found to exist according to the thickness of SiO 2 film and the specific conductivity of Si 3 N 4 film; injection type, ion drift type and mixed type (where only negative charges are stored at the SiO 2 -Si 3 N 4 interface under both polarities of bias voltages). Furthermore, even if the thickness of Si 3 N 4 film is changed with other parameters kept constant, no change of charge storage types is observed. It is considered that there are two discharging mechanisms, namely, the one where stored charges near the interface between SiO 2 and Si 3 N 4 films flow through SiO 2 film into silicon and the other one where the stored charges flow into bulk region of Si 3 N 4 film.