Mitigating cycle-to-cycle variability in Ag/HfO2/W RRAM devices through Plasma-enhanced ALD

The stochastic nature of conductive filament formation remains a primary bottleneck for the reliable operation of Resistive Random Access Memory (RRAM). In this work, we present an experimental study of Pt/Ag/HfO 2 /W/Ti memristive devices, evaluating the impact of the Atomic Layer Deposition growth method (Thermal vs. Plasma-Enhanced). Our analysis indicates that the Plasma-Enhanced Atomic Layer Deposition-grown devices show lower cycle-to-cycle variability than the Thermal Atomic Layer Deposition-grown devices. This reduction in variability yields tightly distributed Set and Reset voltages, and a highly stable memory window, which could be attributed to a more controlled defect density in the plasma-grown oxide that stabilizes the filament formation. To physically justify this improvement and verify the conduction mechanisms, temperature-dependent measurements were performed on the Low Resistance State (LRS) of the Plasma-enhanced devices. Surprisingly, despite the electrochemically active nature of the Ag top electrode, the extracted Temperature Coefficient of Resistance (TCR) for the 10 nm devices ( ∼ 5.3 · 10 − 4 K − 1 ) is significantly lower than the values typically reported for metallic Ag conductive filaments. This suggests that the resistive switching is not dominated by a purely Ag-based ECM mechanism but rather involves a significant contribution from oxygen-vacancy-related transport. This finding may provide the mechanistic foundation to explain why Plasma-Enhanced films (which promote neutral vacancy clusters in contrast to the charged oxygen vacancies promoted by the Thermal process) show reduced cycle-to-cycle variability.