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

Abstract

The impact of H2 gas flow in the reactive sputtering process to 60 nm-thick ferroelectric Al1−x Sc x N films is investigated with x of 0.26 (high-Sc) and 0.12 (low-Sc). Al1−x Sc x N 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.