Tetsu Negishi

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 SiH4/NH3 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 SiH4/NH3 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.