Wake-Up and Fatigue under Electrical Cycling in HfO₂-Based Ferroelectrics: Mechanisms and Strategies toward Reliable...

HfO₂-based ferroelectrics have attracted intensive research interest as promising candidates for next-generation nonvolatile memory, particularly due to their excellent complementary metal-oxide-semiconductor (CMOS) compatibility and scalability. Unlike conventional perovskite ferroelectrics, their ferroelectricity originates from a metastable non-centrosymmetric phase, whose stability is highly sensitive to electrical cycling, defect chemistry, and processing conditions. Consequently, the evolution of ferroelectric properties during repeated electrical operation proceeds through two distinct phenomena, wake-up and fatigue, whose combined progression determines device endurance and reliability. This review covers the physical origins and operating mechanisms of wake-up and fatigue in HfO₂-based ferroelectrics, including oxygen vacancy dynamics and interfacial defect chemistry. Building on these insights, we discuss experimentally demonstrated strategies for controlling these behaviors, including composition and doping engineering, process optimization, electrode and interlayer design, and multilayer structural engineering. The discussion is further extended from materials-level mechanisms to device-level applications, with particular emphasis on how defect redistribution, charge trapping, domain-wall pinning, and cycling-induced phase evolution modify finite-pulse switching kinetics. By correlating defect/phase-transition physics, switching dynamics, and device-level reliability metrics, this review provides design guidelines for the development of reliable HfO₂-based ferroelectric devices.