Atomistic simulations of failure mechanisms in ultrascaled HfO_x RRAM arrays

Abstract: Filamentary Resistive Random Access Memory (RRAM) devices have so far been scaled down to a 2.1 nm feature size, 2 nm thickness, and integrated with advanced transistor nodes for active cell selection. Evaluating their ultimate integration density now involves understanding the scales at which switching can be reliably achieved in matrix-like structures, and the associated failure mechanisms. Previous theoretical studies explored ultrascaled RRAM based on static electronic properties and fixed filament geometry, or continuum or regular domains. While useful, these approaches do not simultaneously capture the underlying structural irregularity of the switching material, and the finite size and number of atoms involved in the switching process, both of which heavily influence the kinetics of atomic relocation and the resulting current flow. Here we leverage a custom atomistic simulation tool designed to capture such effects to investigate the failure mechanisms which emerge in high-density passive RRAM arrays, as well as insight on how they can be mitigated.