Threshold voltage instability on nitride based localized charge trap non-volatile memory devices

For more than 30 years, charge storage based non-volatile memory (NVM) devices such as floating gate (FG) NVM is one of the key enablers in the rapid evolution of modern intelligent consumer electronics. However, incessant technology scaling trend has exposed severe reliability challenges of FG NVM devices. Nitride based charge trap (CT) NVM is one of the most promising candidates to eclipse FG NVM as the mainstream flash memory technology. This is due to the intrinsic immunity to point defects of nitride based CT NVM and its superior device scalability as compared to FG NVM. Due to the aggressive technology scaling trend, nitride based CT NVM devices face reliability challenges in post cycled threshold voltage (Vt) instability. For both FG and nitride based CT NVM devices, post cycled Vt instability induces significant Vt distribution shift and broadening of program cells. Vt distribution shifting and broadening reduce the operating window and premature data retention failures of the charge storage based NVM devices. Vt instability mechanisms of nitride based CTF memory inevitably introduces stochastic fluctuations in Vt of nitride based CTF cells which is detrimental to long term data retention performance. Thus, it is imperative to research and shed new lights in the physical mechanisms of V t instability in nitride based CT NVM devices. Throughout this work, the charge trap dynamics and Vt instability of nitride based CT NVM were meticulously characterized and studied. Stretched Exponential (SE) is applied to model the decay and steady behaviour of Vt distribution shift exhibited on nitride based CT NVM devices. SE function typically models the decay nature of disordered material. In this work, both SE decay phase and steady phase of Vt distribution shift observed on nitride based CT NVM devices were thoroughly studied to understand the charge loss mechanism that is detrimental to its data retention performance.