Endurance/Retention Trade-off on src='/images/tex/20778.gif' alt='hbox {HfO}_{2}/hbox {Metal}'> Cap 1T1R Bipolar RRAM

摘要

The endurance/retention performance of $hbox{HfO}_{2}/break hbox{Metal}$ cap RRAM devices in a 1T1R configuration shows metal cap dependence. For Hf and Ti caps, owning strong thermodynamic ability of extracting oxygen from $hbox{HfO}_{2}$ , long pulse endurance $(>hbox{10}^{10} hbox{cycles})$ could be achieved. For Ta cap, owning lower thermodynamic ability of extracting oxygen from $hbox{HfO}_{2}$, better retention can be achieved. Therefore, an endurance/retention performance tradeoff is identified on the 40 nm $times$ 40 nm $hbox{HfO}_{2}/hbox{Metal}$ cap bipolar RRAM devices. The tradeoff of endurance/retention performance can be explained by a different filament constriction shape depending on metal cap layer as derived from fitting $I$– $V$ curves in the quantum point contact model. This difference in filament constriction shape is attributed to the thermodynamics difference of metal cap: Hf and Ti have a stronger thermodynamical ability to extract oxygen from $hbox{HfO}_{2}$ than Ta. The possibility of tuning the intrinsic reliability performance by changing the cap materials paves a way for optimizing the operation of RRAM devices into the desired specifics.