Nonvolatile memories using deep traps formed in Al₂ O ₃ by metal ion implantation

We demonstrate the feasibility of an approach to nonvolatile memory (NVM) that exploits charge trapping at deep-energy levels formed in Al₂ O₃ by metal doping. Our calculations show that V and Nb are expected to form such deep energy levels in the band gap of Al₂ O₃. To demonstrate the effectiveness of this approach these metal ions were ion-implanted into test structures based on an Al₂ O₃ trapping layer. Several structural analysis techniques and photocurrent spectroscopy show that the doped metal ions are located close to the Al ₂ O₃ / SiO₂ interface and exhibit characteristics consistent with some of the deep levels predicted in calculations. The resulting test devices are shown to exhibit promising NVM characteristics.