Programming-conditions solutions towards suppression of retention tails of scaled oxide-based RRAM

We investigate the impact of pulse programming conditions on data-retention of 40nm × 40nm TiN\HfO2\Hf RRAM devices, focusing on the failure of tail bits. We demonstrate that retention loss tail bit is not due to out diffusion of filament constituents but by low activation-energy (Ea~0.5eV) diffusing species, which are understood as metastable Oxygen (O)-ions in the neighborhood of the conductive-filament constriction. In order to minimize their impact, effective programming pathways are demonstrated, as the low-Ea population is better reduced by (i) using longer Write pulses rather than higher current-pulse amplitudes, and/or by (ii) using shorter reset pulse prior to Write set.