Reactive sputtering of ferroelectric AlScN films with H₂ gas flow for endurance improvement

The impact of H₂ gas flow in the reactive sputtering process to 60 nm-thick ferroelectric Al_1−xSc_xN films is investigated with x of 0.26 (high-Sc) and 0.12 (low-Sc). Al_1−xSc_xN films exhibit clear ferroelectric switching, confirming the robustness against reducing ambient. The dielectric constants (ϵ _i) as well as the leakage current decrease, and the breakdown field (E _BD) increases with H₂ flow. Although the remanent polarization (P _r) decreases with H₂ flow, the wake-up effect is suppressed for the high-Sc film, and the fatigue effect is weakened for the low-Sc film. By probing the change in the coercive field (E _c) after the switching cycle test, we anticipate oxygen impurities bonded to Sc and Al atoms are the source of wake-up and fatigue effects, respectively. As a result, a high endurance cycle of 2 × 10⁷ times was achieved for low-Sc films with H₂ flow.