Comparative studies on ferroelectric switching kinetics of sputtered Hf0.5Zr0.5O2 thin films with variations in film thickness and crystallinity

Abstract

Ferroelectric Hf0.5Zr0.5O2 (HZO) thin film capacitors with Pt/HZO/TiN structures were characterized to investigate the effects of oxygen partial pressure (PO2) and film thickness on the ferroelectric properties and switching dynamics of sputter-deposited HZO thin films. The PO2 during deposition and the film thickness varied from 0% to 1.5% and from 20 to 30 nm, respectively. The ferroelectric remnant polarization (2Pr) was 24.8 μC/cm2 for the 20-nm-thick HZO thin film deposited at a PO2 of 0% and decreased with increasing PO2 and film thickness due to variation in the amount of ferroelectric orthorhombic phase. The 2Pr of the 30-nm-thick HZO film deposited at a PO2 of 1% was 9.60 μC/cm2. The switching times and related parameters of the HZO films were estimated and analyzed by Kolmogorov–Avrami–Ishibashi and nucleation-limited switching (NLS) models. The NLS model provided better fitting results over the full range of polarization switching. The switching times could be modulated with variations in PO2 and film thickness from 0.46 to 1.58 μs. The activation field for polarization reversal increased with increasing PO2, and the degree of PO2 dependence was higher for a thinner film.