Influence of High-Pressure Annealing Conditions on Ferroelectric and Interfacial Properties of Zr-Rich HfₓZr₁₋ₓO₂Capacitors

Abstract

In this study, we have carried out an in-depth analysis on the role of high-pressure annealing (HPA) conditions on ferroelectricity as well as the interfacial property of Hf <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Zr <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (HZO) capacitors in metal-ferroelectric-metal (MFM) structure. Unlike conventional 1:1 HZO films, HZO demonstrates the highest ferroelectricity at 1:3 Hf:Zr ratio in HPA and a significantly higher maximum remanent polarization ( P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> ) of 31 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> was achieved as compared to 19 μC/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> obtained in rapid thermal annealing (RTA) (HZO [1:1]). To understand the influence of HPA conditions, HZO [1:3] capacitors are annealed at various temperatures (300 °C, 400 °C, 500 °C, and 600 °C) and pressures (1, 50, and 200 atm). Ferroelectricity in HZO is found to enhance with increasing HPA temperature or pressure due to higher ferroelectric phase formation as revealed by grazing incidence X-ray diffractometer (GIXRD) analysis. Transient pulse switching measurement suggests the reduction in the effective thickness of the interfacial nonferroelectric film at a high HPA temperature or pressure which was also validated by impedance analysis. Further, impedance analysis reveals a reduction in the number of oxygen vacancy defects with increasing annealing temperature or pressure implying a phase transition from the tetragonal phase of nonferroelectric layer to the ferroelectric orthorhombic phase. In addition, excellent endurance property till 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9</sup> cycles with reduced wake-up effect was observed in HZO [1:3] capacitors with increasing the HPA temperature, while higher annealing pressure is found to increase P <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> without affecting its endurance property. The results obtained herein can be of significant scientific importance, especially to achieve enhanced ferroelectric property with reduced wake-up effect in Zr-rich HZO ferroelectrics.