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.