Improved multi-level control of RRAM using pulse-train programming

Multi-level cell (MLC) capability in RRAM is attractive for reducing the cost per bit. Based on the filamentary switching mechanisms, we propose a pulse-train programming scheme to achieve reliable and uniform MLC controls without the need of any read-verification operation. By applying the novel scheme to a 3 bit/cell RRAM device, the uniformity of resistance distribution can be improved up to 80%.