Ferroelectric recovery of scaled-down Y-doped HfO₂ thin films on NiSi₂ after annealing

In this work, the ferroelectric properties of Y-doped HfO₂ (YHO) thin films with a physical thickness ranging from 42 nm to 7.4 nm deposited on NiSi₂ are reported. Ferroelectricity in scaled-down YHO is heavily impacted by the following factors: (1) depolarizing fields developed at non-ferroelectric interfacial layers whose thickness is dependent on annealing conditions and (2) the increasingly larger leakage current that develops in thinner YHO films. The lowest remanent polarization (P_r) is obtained in thinner YHO films since the non-ferroelectric interfacial layer and the total leakage current introduce larger contributions towards the lack of control on dipoles' switching dynamics and, therefore, the final P_r. Nevertheless, by adjusting annealing conditions, even thinner YHO films can gradually recover their ferroelectric properties; thus, a simple trade-off between the YHO annealing temperature and leakage current could help in the recovery of P_r in YHO-based thinner films.