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

The impact of H-2 gas flow in the reactive sputtering process to 60 nm-thick ferroelectric Al1-xScxN films is investigated with x of 0.26 (high-Sc) and 0.12 (low-Sc). Al1-xScxN films exhibit clear ferroelectric switching, confirming the robustness against reducing ambient. The dielectric constants (epsilon(i)) as well as the leakage current decrease, and the breakdown field (E-BD) increases with H-2 flow. Although the remanent polarization (P-r) decreases with H-2 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 x 10(7) times was achieved for low-Sc films with H-2 flow.