On the Origin of Low-Resistance State Retention Failure in HfO₂-Based RRAM and Impact of Doping/Alloying

We study in detail the impact of alloying HfO2with Al (Hf1_xAl2xO2+x) on the oxide-based resistive random access memory (RRAM) (OxRRAM) thermal stability through material characterization, electrical measurements, and atomistic simulation. Indeed, migration of oxygen atoms inside the dielectric is at the heart of OxRRAM operations. Hence, we performed comprehensive diffusion barrier calculations in HfO2, Hf1_xAl2xO2+x, and Hf1_xTixO2relative to the oxygen vacancy (Vo) movement involved in low-resistance state (RON) thermal stability. Calculations are performed at the best level using ab initio techniques. This paper provides an insight on the improved RON stability of our Hf1_xAl2xO2+x-based RRAM devices and predicts the degraded retention of Hf1_xTixO2-based RRAM measured in the literature. Our theoretical calculations link the origin of RON retention failure to the lateral diffusion of oxygen vacancies at the constriction/tip of the conductive filament in HfO2-based RRAM.