Switching Kinetics Control of W-Based ReRAM Cells in Transient Operation by Interface Engineering

Tungsten (W) is one of the most promising materials to be used in resistive random-access memory electrodes due to its low work function and compatibility with semiconductors, which raises the possibility of device integration, scalability, and low power consumption. However, W has multiple oxidation states that affect device reliability, due to the formation of semistable oxides at the switching interface. W chemical interaction is modulated through the insertion of Al2O3 or Ti interfacial layers. The time-dependent switching kinetics are investigated in transient Set/Reset operations. It is observed that a compact and stoichiometric atomic-layer-deposited Al2O3 barrier layer completely prevents W oxidation, resulting in a sharp current transient. The use of a sputtered Ti buffer layer allows a partial W oxidation, defining a tunable high-resistance state by pulse rise time control. Notable improvements in endurance, power consumption, resistance state stabilization, and cycle-to-cycle and device-to-device variability are reported. Switching kinetics and conductive nanofilament evolution are studied in detail to understand the microscopic effect of the interface modifications. The tunability of multi-HRS states by pulse timing control in Pt/HfO2/Ti/W is in the interest of network and brain-inspired computing applications, adding a degree of freedom in the modulation of its resistance.