Interface engineered HfO₂-based 3D vertical ReRAM

We demonstrate a double-layer 3D vertical resistive random access memory (ReRAM) stack implementing a Pt/HfO₂/TiN memory cell. The HfO₂ switching layer is grown by atomic layer deposition on the sidewall of a SiO₂/TiN/SiO₂/TiN/SiO₂ multilayer pillar. A steep vertical profile was achieved using CMOS-compatible TiN dry etching. We employ in situ TiN bottom interface engineering by ozone, which results in (a) significant forming voltage reduction which allows for forming-free operation in AC pulsed mode, and (b) non-linearity tuning of low resistance state by current compliance during Set operation. The vertical ReRAM shows excellent read and write disturb immunity between vertically stacked cells, retention over 10⁴ s and excellent switching stability at 400 K. Endurance of 10⁷ write cycles was achieved using 100 ns wide AC pulses while fast switching speed using pulses of only 10 ns width is also demonstrated. The active switching region was evaluated to be located closer to the bottom interface which allows for the observed high endurance.