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 Hf0.5Zr0.5O2 thin films 8 nm thick incorporated into a metal-ferroelectric-metal capacitor are fabricated and characterized with varying thicknesses of an Al2O3 interfacial layer. The magnitude of the depolarization field is adjusted by controlling the thickness of the Al2O3 layer. The initial polarization and the change in polarization with electric field cycling is strongly impacted by the insertion of Al2O3 within the device stack. Transient polarization loss is shown to get worse with larger depolarization fields and data retention is evaluated up to 85 degrees C.