Demonstration of Highly Robust 5 nm Hf0.5Zr0.5O₂ Ultra-Thin Ferroelectric Capacitor by Improving Interface Quality

In this letter, 5 nm-thick HZO ultra-thin ferroelectric capacitors with excellent remanent polarization ( $\text{P}_{\mathrm {r}}$ ) 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 $\text{P}_{\mathrm {r}}$ of $20.5~\mu \text{C}$ /cm2 (i.e. 2P $_{\mathrm {r}}= 41\,\,\mu \text{C}$ /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 $_{\mathrm {r}}$ value higher than $20~\mu \text{C}$ /cm2 after 1010 cycles at a high electric field of 5 MV/cm without breakdown, though the $\text{P}_{\mathrm {r}}$ 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.