Ferroelectric Hf1-xZrxO2 memories: device reliability and depolarization fields

The influence of depolarization and its role in causing data retention failure in ferroelectric memories is investigated. Ferroelectric Hf _0.5 Zr _0.5 O ₂ thin films 8 nm thick incorporated into a metal-ferroelectric-metal capacitor are fabricated and characterized with varying thicknesses of an Al ₂ O ₃ interfacial layer. The magnitude of the depolarization field is adjusted by controlling the thickness of the Al ₂ O ₃ layer. The initial polarization and the change in polarization with electric field cycling is strongly impacted by the insertion of Al ₂ O ₃ within the device stack. Transient polarization loss is shown to get worse with larger depolarization fields and data retention is evaluated up to 85 °C.