Demonstration of Highly Robust 5 nm Hf_0.5Zr_0.5O₂ Ultra-Thin Ferroelectric Capacitor by Improving Interface Quality

In this letter, 5 nm-thick HZO ultra-thin ferroelectric capacitors with excellent remanent polarization (P_r) and reliability are presented. The TiN/HZO/TiN metal-ferroelectric-metal (MFM) capacitor stack was deposited consecutively in the same atomic layer deposition (ALD) system without breaking the vacuum (i.e. “in-situ” like) to improve the interface quality between TiN electrodes and HZO ferroelectric layer. The samples show high P_r of 20.5 µC/cm² (i.e. 2P_r = 41 µC/cm²) under driving voltage of 3 V with low coercive voltage of approximately 0.6 V. The robustness of the MFM capacitor was presented by the outstanding endurance characteristics for keeping 2P_r value higher than 20 µC/cm² after 10¹⁰ cycles at a high electric field of 5 MV/cm without breakdown, though the P_r values gradually degrade with cycles at low field (i.e. 2.4 MV/cm). The highly robust endurance characteristics of the 5nm-thick HZO MFM capacitor indicate the good interface quality achieved in this study.