Ferroelectric and field-induced ferroelectric phase formation in atomic-layer-deposited ZrO2 thin films with TiN electrodes†

Abstract

This study investigates the origin of ferroelectric (FE) phase formation in 10-nm-thick atomic-layer-deposited ZrO₂ thin films by examining their structure and electrical properties as a function of deposition temperature (T_dep, 280–310 °C) and post-metallization annealing (PMA) steps. Polarization measurements revealed only field-induced ferroelectric (FFE) properties in the films deposited at 280 °C. However, the FE-like properties were observed in the films deposited at T_dep = 285–310 °C, with double remnant polarization (2P_r) values of ∼15 μC cm⁻² at 310 °C, where the films exhibited improved crystallinity, larger grain size, and higher oxygen density. However, PMA led to increased oxygen deficiency, causing FE characteristics to vanish, leaving only FFE in the films. In addition, the wake-up process does not correspond to the permanent phase transition from the non-polar tetragonal phase to the polar orthorhombic phase. Rather than that, the internal field, induced by the asymmetric oxygen vacancy distribution across the film thickness, undergoes disparate evolution with the cycling in the FE and FFE regions in the film. The overall FE-like property of the woken-up state corresponds to the merged FE and FFE properties, which are also influenced by the applied electric field (E_app) strength during the cycling and property measurements.