Suppression of Oxide and Interface Charge Density in Radio Frequency Sputtered Ta2O5 Thin Films

Abstract

To replace SiO2 as gate dielectrics in complementary metal‐oxide‐semiconductor‐compatible microelectronic devices, research on alternative high‐k dielectric materials is deeply focused. Although high‐k dielectrics have high permittivity, it suffers from poor electrical quality due to the presence of charge densities during the deposition process. To suppress these charge densities, there is an urge for a suitable fabrication process. Herein, radio frequency magnetron sputtering is used to deposit Ta2O5 thin films on p‐type Si. During deposition, sputtering pressure and Ar/O2 gas flow ratio are varied systematically. Postdeposition annealing is carried out for an hour at 900 °C in air ambient. The microstructural, morphological, and electrical properties are studied from X‐ray diffraction (XRD), Fourier transform infrared spectroscopy, atomic force microscopy (AFM), capacitance–voltage, and current–voltage characteristics. XRD reveals orthorhombic β‐phase structure of the film annealed at 900 °C. The AFM micrographs show that the roughness of the film increases with the increase in both sputtering pressure and Ar/O2 gas flow ratio. The oxide charge density (Qox), interface charge density (Dit), and leakage current are found to be decreased with the increase in both Ar/O2 gas flow ratio and sputtering pressure.