Effect of Annealing Ferroelectric HfO2 Thin Films: In Situ, High Temperature X‐Ray Diffraction

The ferroelectricity in fluorite oxides has gained increasing interest due to its promising properties for multiple applications in semiconductor as well as energy devices. The structural origin of the unexpected ferroelectricity is now believed to be the formation of a non‐centrosymmetric orthorhombic phase with the space group of Pca21. However, the factors driving the formation of the ferroelectric phase are still under debate. In this study, to understand the effect of annealing temperature, the crystallization process of doped HfO2 thin films is analyzed using in situ, high‐temperature X‐ray diffraction. The change in phase fractions in a multiphase system accompanied with the unit cell volume increase during annealing could be directly observed from X‐ray diffraction analyses, and the observations give an information toward understanding the effect of annealing temperature on the structure and electrical properties. A strong coupling between the structure and the electrical properties is reconfirmed from this result. The phase evolution in ferroelectric hafnia thin films during crystallization annealing is elucidated using high temperature in situ X‐ray diffraction technique. The effect of postdeposition annealing on the structure and ferroelectric properties can be understood based on the in situ observations. This study provides an insight into understanding and optimizing the hidden crystallization process of fluorite‐type ferroelectrics.