Engineering the dielectric properties of t-HfO2 thin films using first-principles calculations

Abstract

Hafnium oxide (HfO₂) is a promising microelectronic material for the integrated circuit industry due to its high dielectric constant (k value) and wide bandgap. However, the high-k properties of HfO₂ are typically associated with a metastable tetragonal phase (t-HfO₂), and the mechanisms influencing its dielectric behavior remain unclear. In this paper, we explore the impact of thickness, strain, and interfacial interaction on the dielectric properties of t-HfO₂ thin films using first-principles calculations. Our results show that the dielectric constant increases with film thickness and is maintained under the effect of the interfacial interaction from HfO₂/ZrO₂ interfaces. The 5-layer (5L) t-HfO₂ film achieves a high in-plane dielectric constant of 244, and the 1-layer (1L) t-HfO₂ film exhibits an equivalent oxide thickness (EOT) of 7.14 Å. Additionally, a specific range of tensile strain enhances the dielectric constant and shifts the main peak of dielectric function to lower photon energies, which can be attributed to the softening of phonon modes. Such atomically thin t-HfO₂ films exhibit potential for achieving high capacitance and provide an important path for realizing high-performance memory devices.