Multiphysics Simulation of Bipolar Filamentary Resistive Switching by Coupling Phase-Field and Electrothermal Models

The most challenging part of the device simulation of resistive memory is dealing with the behaviors of the conductive filament (CF). In the case of bipolar switching by valence-change mechanism, the evolution of the CF is determined by the formation, annihilation, and migration of anion vacancies in the switching material which is usually a transition metal oxide. The CF and matrix are defective and non-defective phases with low and high resistance, respectively. Starting from a pristine state with a completely non-defective phase, the CF is formed, ruptured, and reconnected by applied biases.<br/>In this presentation, we demonstrate our device simulation model capable of simulating a full switching cycle comprising forming, reset, and setting operations. Also, our simulation can model data retention. The phase-field model is adopted to represent a system with two phases: defective and non-defective, i.e., CF and matrix phases. The Cahn-Hilliard equation deals with the evolution of the two-phase system. The phase-field and electrothermal models are coupled in a finite-element package, COMSOL Multiphysics. The bipolar switching system is described as a metal-insulator-metal structure where the top interface has a constant vacancy concentration, implying that the oxygen-deficient top interface can be a sink for incoming vacancies resulting in the disappearance of the CF while it can be a source for outgoing vacancies resulting in the growth of the CF. The initial condition must include some perturbation in the system such as a pre-existing defect, interface roughness, and so on.<br/>The central advantage of our model over other device simulations is that our model can predict the shape of the CF for different physical conditions including material properties, device architecture, initial defect configuration, and bias conditions. A CF area is not pre-defined. Our simulation can start from the forming operation and can repeat multiple reset-set cycles. More details will be shown in the actual presentation.