Impacts of Post Annealing Process on the Ferroelectric Properties of Aluminum-doped Hafnium Oxide

Abstract

Ferroelectric-based thin films are considered promising in both memory and logic devices due to their intrinsic characteristic of spontaneous remanent polarization that can be reversed by the applied external electric field. Recently, the evolution of HfO2-based ferroelectric thin films has revolved around understanding the structural investigations and how to improve ferroelectric properties by controlling dopants composition, thin film thickness, top electrode, post annealing conditions and so on. Based on the theories so far, HfO2-based thin films generally have been crystalized by thermal treatment at a higher temperature than the deposition process in order to induce ferroelectric-related non-centrosymmetric orthorhombic phase then show ferroelectric properties due to the difference of the thermal expansion coefficient with substrates. Phase transition within the thin film is believed to happen under certain tensile stress from a capping layer and annealing treatment conditions. Therefore, further studies are required regarding post-annealing and metal capping layer engineering on the ferroelectric HfO2 thin film.