Endurance/Retention Trade-off on $\hbox{HfO}_{2}/\hbox{Metal}$ Cap 1T1R Bipolar RRAM

Abstract

The endurance/retention performance of HfO ₂ / 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 HfO ₂ , long pulse endurance (>10 ¹⁰ cycles) could be achieved. For Ta cap, owning lower thermodynamic ability of extracting oxygen from HfO ₂ , better retention can be achieved. Therefore, an endurance/retention performance tradeoff is identified on the 40 nm × 40 nm HfO ₂ /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 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.