Nonvolatile analog memory in MNOS capacitors

Long-term storage of analog signals of wide dynamic range has been successfully demonstrated for the first time in single MNOS capacitors. After a reset state is established by majority carrier tunneling, measured pulses of light are used to generate minority carriers which tunnel to nitride traps and in turn induce shifts in the flat-band voltage proportional to the minority carrier charge. Linear voltage windows of 12 volts are observed, and logarithmic decay rates are as low as 30 mV per decade of storage time per volt of initial flat-band shift. Analog signals can be stored linearly over a dynamic range of 40 dB for 30 hours.