Soft X-Ray Absorption Spectroscopy Investigation of HfO2 and ZrO2 Thin Films with Modulated Crystalline Phase by Varying Dopants (Al, Si, Gd) for Ferroelectric and High-k Dielectric Applications

Abstract

The results of a study on the effects of aluminum (Al), silicon (Si), and gadolinium (Gd) dopants on controlling the crystal phases of hafnium (Hf) and zirconium (Zr) oxide thin films using soft X-ray absorption spectroscopy (XAS) are presented. The Al and Si dopants increase the orthorhombic phase content in HfO2, which is favorable for ferroelectric properties, while Gd dopants are advantageous for the tetragonal phase in ZrO2 formation which is beneficial for high dielectric constant properties. X-ray absorption near-edge spectroscopy analysis of O K-edge and Zr L2,3-edge is used to identify changes in crystal phases and electronic structures due to each dopant in comparison with simulations. The experiments include fabrication of HfO2, ZrO2 films by atomic layer deposition and the crystalline phase analysis results are compared using various analytical techniques such as X-ray diffraction, XAS, and direct current sweep to clarify the effects of the dopants. In conclusion, this work demonstrates that selecting appropriate dopants can optimize the properties of HfO2 and ZrO2 thin films for specific applications.