CMOS-Compatible ScAlN Ferroelectric Thin Films with Enhanced Polarization for High-Performance FeFET Memory and Artificial Synapses.

ScAlN is an emerging nitride ferroelectric material that exhibits exceptional remnant polarization (P_r) at ultrathin scales (<50 nm), stable single-phase ferroelectricity, and CMOS compatibility, making it highly promising for next-generation low-power, high-density memory and neuromorphic devices. However, ScAlN films deposited by conventional physical vapor deposition (PVD) faces challenges such as Sc precipitation and crystal orientation degradation at high Sc concentrations (>20%) and reduced thicknesses, leading to deteriorated ferroelectricity and increased leakage. In this work, it is demonstrated that an optimized substrate structure enables PVD-grown Sc_0.2Al_0.8N films to achieve significantly enhanced ferroelectric properties compared to conventional substrates, retaining high P_r even at 20 nm thickness. This improvement is further validated with Sc_0.3Al_0.7N and Sc_0.35Al_0.65N films across varying thicknesses. Additionally, a Sc_0.2Al_0.8N-based FeFET fabricated on this substrate exhibits a 17 V memory window, >10³ switching ratio, >10⁴ s retention, and >10⁴ cycle endurance. When configured as an artificial synapse, the device achieves 98.7% recognition accuracy in neural network training under encoded pulse voltages, highlighting its potential for energy-efficient computing.