Evolution of crystallographic structure and ferroelectricity of Hf0.5Zr0.5O2 films with different deposition rate

Abstract

Hf0.5Zr0.5O2 films are one of the most attractive HfO2-based ferroelectric films because of good ferroelectricity, extreme thinness, and excellent compatibility with silicon devices. The origin of the ferroelectricity of Hf0.5Zr0.5O2 films is the noncentrosymmetric orthorhombic phase (space group Pca21). The effects of process temperature, annealing temperature, thickness, and doping to increase the portion of the orthorhombic phase, which contributes to ferroelectricity, have been studied extensively. However, although most studies have used atomic layer deposition, no study has been reported on the effect of the deposition rate on the ferroelectricity of Hf0.5Zr0.5O2 films. In this work, the influences of the deposition rate on the ferroelectricity and crystal structure of Hf0.5Zr0.5O2 films were examined. In order to conduct systematic and quantitative analysis, measurements of switching transient current, ferroelectric P-E curve, dielectric constant, deconvolution of grazing angle incidence X-ray diffraction, and piezoresponse force microscopy were performed. Hf0.5Zr0.5O2 films with a deposition rate of 1.1 Å/cycle have a more ideal hysteresis curve shape, higher remanent polarization (initial state: 16 μC/cm2, wake up state: 22 μC/cm2), and a higher orthorhombic phase portion than other deposition rates.