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 (E_a~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-E_a 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.