Scaling perspective and reliability of conductive filament formation in ultra-scaled HfO2 Resistive Random Access Memory

In this paper we report about the scaling perspective of ultra-scaled HfO2 Resistive Random Access Memory devices. Due to filamentary conduction, the scalability of these devices is considered to be ultimately limited by the size of the conductive filament. However, even though the precise size and shape of the filament is not fully elucidated, it is widely accepted that its size is mainly controlled by the current compliance. In turn, the latter sets the operating current level of the cell. The reduction of the current level is nevertheless accompanied by performance instabilities, which are the main reliability threat for low-current operations. The resulting tradeoff raises concerns about the scalability potential of RRAM devices. In this work, we combine device-level measurements, Conductive Atomic-Force Microscopy (C-AFM), and physics-based simulations of HfO2 RRAM devices to elucidate the reason for these instabilities. Results clarify the scaling perspectives of ultra-low cell size (< 10×10 nm2) RRAMs and their reliability.