Direct growth of ferroelectric orthorhombic ZrO₂ on Ru by atomic layer deposition at 300 °C

Fluorite-structured binary oxide ferroelectrics exhibit robust ferroelectricity at a thickness below 10 nm, making them highly scalable and applicable for high-end semiconductor devices. Despite this promising prospect, achieving highly reliable ferroelectrics still demands a significant thermal budget to form a ferroelectric phase, being a hurdle for their use in high-end complementary metal oxide semiconductor (CMOS) processing. Here, we report a robust ferroelectric behavior of an 8 nm-thick ZrO₂ film deposited via plasma-enhanced atomic layer deposition at 300 °C on a (002)-oriented Ru without any post-annealing process, demonstrating high compatibility with CMOS processing. We propose that a plausible mechanism for this is the local domain matching epitaxy based on the high-resolution transmission electron microscopy and piezoelectric force microscopy results, where the templating effect between [101]-oriented grains of orthorhombic ZrO₂ and [010]-oriented grains of Ru enables the direct growth of ferroelectric ZrO₂. The 2P_r value is 20 μC cm^-2, and it can be further improved by post-annealing at 400 °C to 23 μC cm^-2 without showing the wake-up behavior. Ferroelectric switching shows stable endurance for up to 10⁹ cycles, showcasing its high potential in CMOS-compatible applications and nanoelectronics with a low thermal budget.