Elucidating Postprogramming Relaxation in Multilevel Cell-Resistive Random Access Memory by Means of Experimental and Kinetic Monte Carlo Simulation Data

This work explores the phenomenon of HfO2 resistive random access memory (RRAM) postprogramming resistance relaxation using experimental data and kinetic Monte Carlo (KMC) physical simulation. This issue has become an important limitation for multilevel cell (MLC) applications. The physical KMC simulation replicates the RRAM cell-to-cell intrinsic resistance variability due to the conductive filament (CF) morphology fluctuations and the weak correlation between the number of oxygen vacancies and the resulting resistance. It furthermore accurately simulates the vacancies' microscopic dynamics within the CF that are responsible for the RRAM resistance relaxation. A link between programming current, CF size/configuration, and relaxation amplitude is clarified and shows the ensuing benefits and limitations of smart programming techniques (read & verify) for MLC applications. Coupled with experimental data obtained on HfO2-based RRAM arrays, this simulation paves the way to a better understanding of the physics at stake in the RRAM relaxation process and provides guidelines to potential technological solutions for MLC reliability prediction.