Electron injection characteristics of MNOS nonvolatile semiconductor memory structure using the reverse breakdown of the PN junction

Abstract

AbstractIn this paper, we describe an improved carrier injection method for the metal nitride‐oxide semiconductor (MNOS) structure, which is a prospective nonvolatile semiconductor memory device. The investigation is based on the prediction that carrier injection should be improved by increasing the carrier density at the Si surface and by lowering the tunneling barrier height of the SiO2 and that these conditions should be realizable by using the current flow due to reverse breakdown of the pn junction near the channel region of the Si surface under the gate electrode.Experiments indicate that the flatband voltage shift in the presence of electron injection is large as a result of the reverse breakdown current of the pn junction. Electron injection was further improved by an additional lowering of the tunneling barrier height associated with the voltage drop across the resistance connected to the bias circuit of the pn junction. This voltage drop was produced by the current flow due to reverse breakdown of the pn junction.Faster, stronger carrier injection from the Si surface to the traps in the insulator of MNOS structure can be realized by optimizing the doping densities in p and n regions and optimizing the resistance connected to the pn biasing circuit. This method is useful for electrical erasable nonvolatile semiconductor memory (EEPROM) devices without voltage up‐converter circuits.