Benefit of Al2O3/HfO2 bilayer for BEOL RRAM integration through 16kb memory cut characterization

In this paper, for the first time, the reliability of HfO₂-based RRAM devices integrated in an advanced 28nm CMOS 16kbit demonstrator is presented. The effect of the introduction of a thin Al₂O₃ layer in TiN/Ti/HfO₂/Al₂O₃/TiN is explored to improve the memory performances. Thanks to the in-depth electrical characterization of both HfO₂ and HfO₂/Al₂O₃ stacks at device level and in the 16×1kbit demonstrator the interest of the bilayer is put forward (endurance: 1 decade after 1M cycles and retention: 6 hours at 200°C). Finally, thanks to our 3D model based on calculation of the Conductive Filament resistance using trap assisted tunneling (TAT) the role of Al₂O₃ as tunneling layer is highlighted.