Monolithic integration and ferroelectric phase evolution of hafnium zirconium oxide in 2D neuromorphic synaptic devices

Hafnium zirconium oxide (HZO)-based ferroelectric field-effect transistors (FeFETs) are three-terminal devices with attractive properties for embedded memory and in-memory computing architectures. We probe the HZO ferroelectric landscape dynamics with materials characterization, device modeling, and electrical measurements. Metal-ferroelectric-metal capacitors fabricated with HZO with Pt contacts were processed at complementary metal-oxide-semiconductor (CMOS)-compatible temperatures near 450 °C. We found that the HZO films do not require field processing for ferroelectricity to arise and have an average remnant polarization between 10 and 20 μC/cm2 and a coercive field of ∼0.6 MV/cm. The average HZO grain sizes range from 10 to 15 nm and closely follow the ferroelectric domain size range of 10–20 nm. We further examine the HZO properties by integrating them into back-end-of-the-line (BEOL) FeFET device architectures with WSe2, a prototypical van der Waals system, and verify their robust synaptic plasticity within a 3.5 order of magnitude conductive range. These discoveries highlight a roadmap for material processing, dimensional scaling, and integration of HZO-based FeFETs.