Influences of Voltage Cycling on Variations in HfO 2 -based 3D Trench FeRAM

In this work, we experimentally investigated the variation behavior of HfO2-based 3D trench ferroelectric random access memory (FeRAM) under different voltage cycling conditions. The remanent polarization (Pr) and coercive field (Ec) were extracted to evaluate device-to-device (D2D) and cycle-to-cycle (C2C) variations. The planar-dominated capacitors showed a gradual decrease in variation when the cycling voltage and number increased. In contrast, the trench-dominated capacitors showed irregular changes during cycling. To understand the cause, cross-sectional transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) analyses were performed. The results revealed that the ferroelectric layer at the trench sidewall was thinner and suffered from strong interdiffusion between the electrode and ferroelectric materials. These structural and compositional differences degrade the ferroelectric quality and lead to larger variation in trench-dominated devices. This work clarifies the relationship between cycling behavior and variability in 3D FeRAMs and provides guidance for improving their reliability through interface and material engineering.