Designing cryo-compatible ferroelectric hafnia devices through electrode and interface control

Ferroelectric hafnium zirconium oxide (HZO) is a promising material for next-generation electronic devices due to its excellent scalability and compatibility with complementary metal-oxide-semiconductor processing. As quantum and cryogenic memory applications demand reliable low-temperature performance, the development of stable cryogenic ferroelectrics is becoming increasingly critical. To address this need, we propose a ferroelectric capacitor architecture optimized for cryogenic compatibility. Electrical characterization of asymmetric Pt/HZO/TiN and symmetric Pt/HZO/Pt capacitors show that devices with TiN electrodes experience severe degradation below −125 °C, including asymmetric coercive voltage shifts and collapsed polarization-voltage hysteresis profiles, while Pt/HZO/Pt symmetric devices maintain stable switching down to −175 °C. X-ray photoelectron spectroscopy revealed a TiO_xN_y interlayer at the HZO/TiN interface, absent in Pt devices. This oxidized TiN layer exhibits carrier freeze out at low temperatures, causing the anomalous behavior. Our findings highlight the importance of electrode materials and interface chemistry for achieving reliable cryogenic ferroelectric devices, guiding future strategies to optimize performance for low-temperature environments.