Effects of plasma power on ferroelectric properties of HfO2-ZrO2 nanolaminates produced by plasma enhanced atomic layer deposition

Abstract

This study introduces the use of plasma-enhanced atomic layer deposition (PEALD) for growing ultrathin Zr-doped hafnium oxide (HfO2-ZrO2 or HZO) nanolaminates and the effect of radio frequency (RF) plasma power on the electrical properties of these fluorite-structure oxide films, which were employed in ferroelectric devices. The effect of the PEALD plasma power in a range of 50∼200 W on the degree of the orthorhombic phase and the number of oxygen vacancies in the crystallized films can be found more clearly after the additional heat treatment by rapid thermal annealing (RTA). Our measurement results reveal the notable effect of plasma power in using PEALD on the growth and properties of ferroelectric oxide films. Particularly, the increased plasma power can decrease the crystallized films' remnant polarization (Pr) from 12.68 to 4.29 μC/cm2. Besides, a relationship between the leakage current and the electronic structure causing the films’ polarization is revealed. The spectroscopically resolved band-edge electronic revealed the conversion of orthorhombic HfO2 in the laminar stacking with ZrO2 to the homogeneous HfZrxOy compounds as increasing RF power. In general, these findings show the opportunity to utilize our developed HZO nanolaminates grown by PEALD for many trending applications, particularly polarization-driven memory and ferroelectric-based advanced transistors.