Comprehensive Reliability Assessment of WO_x Engineering for Temperature-Resilient HfZrO₂ FeCAP

HfZrO₂ (HZO) ferroelectric capacitors (FeCAPs) for non-volatile memory are typically formed on the W-plug bottom electrode (BE). We present direct evidence of non-stoichiometric WOx formation even at 350°C thermal budget during post-deposition annealing (PMA) to realize ferro electricity in HZO. To address this, we introduced sputtered amorphous WO interlayer (IL) engineering. Through systematic investigation, we revealed how the physical and chemical properties of WO ILs are related to polarization in the HZO and endurance even in cryogenic environments. More specifically, leveraging 10 nm quasi-stoichiometric WO_2.8 IL not only alleviates leakage path due to oxygen vacancies (V_os) near the BE interface but also facilitates ferroelectric domain formation in the HZO, which is validated by stronger diffraction peak intensity for orthorhombic (o)-phase. This results in a remnant polarization (Pr) greater than 20 μC/cm² after 10⁵ cycles at 123 K in the optimized 10 nm HZO/10 nm WO2.8 IL FeCAP.