Top electrode modulated W/Ag/MgO/Au resistive random access memory for improved electronic synapse performance

Abstract

Resistive random access memory (ReRAM) is touted to replace silicon-based flash memory due to its low operating voltage, fast access speeds, and the potential to scale down to nm range for ultra-high density storage. In addition, its ability to retain multi-level resistance states makes it suitable for neuromorphic computing application. Here, we develop a cationic ReRAM with a sputtered MgO as the insulating layer. The resistive switching properties of the Ag/MgO/Au ReRAM stack reveal a strong dependence on the sputtering conditions of MgO. Due to the highly stable sputtered MgO, repeatable resistive switching memory is achieved with a low ON voltage of ∼0.7 V and a memory window of ∼1 × 105. Limiting Ag diffusion through a modified top electrode in the W/Ag/MgO/Au stack significantly reduces the abruptness of resistive switching, thereby demonstrating analog switching capability. This phenomenon is evident in the improved linearity and symmetry of potentiation and depression weight modulation pulses, demonstrating ideal Hebbian synaptic learning rules.