Large scale integration of MNOS devices

Silicon dioxide is highly permeable to moisture. Impurity ions such as sodium ions can migrate through the oxide. Because of these and other inherent disadvantages of silicon dioxide, silicon nitride has been used. But it is found that silicon-silicon nitride interface has inherent charge instability. This has been overcome by using a layer of silicon dioxide between silicon and silicon nitride. A dual 25-bit 4-phase shift register has been built using MOS and MNOS devices. Pyrolytic and thermal oxides have been used on