Study of localized tunnel oxide degradation after hot carrier stressing using a novel mid-bandgap voltage characterization method

Hot carrier damage, especially by hot holes, limits the reliability performance of nonvolatile memories (NVMs). The damage creates localized traps in the tunnel oxide and localized interface traps at the oxide/silicon interface. In this paper, we propose a novel method to independently quantify trapped charges localized in the oxide and at the interface. We applied the new method to probe the oxide degradation in nitride trapping memory and found (i) the oxide traps (N_OT) capture both electrons and holes, (ii) the retention degradation involves interface trap (N_IT) annealing, electron de-trapping, and hole de-trapping, (iii) upon baking, N_IT annealing and electron de-trapping happen simultaneously while hole de-trapping dominates the long-term instability at 250degC, (iv) the V_T instability can be improved by using an interface strengthening nitridation process.