Electron spin resonance and photoluminescence study of charge trap centers in silicon nitride films and fabrication of proposed oxide-nitride-oxide sidewall 2-bit/cell nonvolatile memories

We have proposed a novel oxide-nitride-oxide (ONO)-sidewall 2-bit/cell nonvolatile memory and fabricated 70-nm-node nonvolatile memory devices. For low-pressure chemical-vapor-deposition (LPCVD)-SiN films, with increasing SiH(4)/NH(3) mixture gas ratio, we have found from ESR and PL evaluation that the paramagnetic defect density increases and some PL emission energy levels become deeper. We consider that the energy-level shift is due to the effects of trap potential overlapping, where the trap centers are generated at the excess silicon atoms in the SiN films. In this study, a SiH(4)/NH(3) mixture gas ratio of less than 1 : 100 was used to suppress the potential overlapping. As a result, we have also shown that the proposed memory device has high performance and excellent scalability.