Investigation of Recovery Phenomena in Hf_0.5Zr_0.5O₂-Based 1T1C FeRAM

Abstract

We have previously studied fatigue and its recovery phenomenon on 64 kbits hafnium-based one-transistor and one-capacitor (1T1C) ferroelectric random-access memory (FeRAM) with PVD-TiN (30 nm)/ALD- Hf0.5Zr0.5O2 (8 nm)/CVD-TiN (50 nm) capacitors. In this study, we characterized a single large capacitor fabricated using the same process as the 1T1C FeRAM to clearly understand the recovery mechanism and comprehensively qualify the recovery effect. The results reveal that the recovery effect is caused by domain depinning and new domains switching owing to a redistribution of oxygen vacancy. Furthermore, it is evident from recovery voltage and recovery pulse width dependence of the recovery effect that the recovery voltage can be reduced by applying a longer recovery pulse width. This enables a more flexible circuit design of 1T1C FeRAM when the recovery method is applied to enhance the cycling endurance.

Keywords

• Capacitor
• hafnium oxide
• ferroelectric random-access memory
• recovery
• zirconium oxide