Microstructure, optical, electrical properties, and leakage current transport mechanism of sol–gel-processed high-k HfO2 gate dielectrics

Abstract Deposition of high- k HfO 2 gate dielectric films on n-type Si and quartz substrates by sol–gel spin-on coating technique has been performed and the structural, optical and electrical characteristics as a function of annealing temperature have been investigated. The structural and optical properties of HfO 2 thin films related to annealing temperature are investigated by X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–vis), and spectroscopic ellipsometry (SE). Results indicate that the monoclinic form of HfO 2 appears when temperature rises through and above 500 °C. The reduction in band gap is observed with the increase of annealing temperature. Moreover, the increase of refractive index ( n ) and density and the decrease of the extinction coefficient with the increase of annealing temperature are obtained by SE measurements. Additionally, the electrical properties based on Al/Si/HfO 2 /Al capacitor are analyzed by means of the high frequency capacitance–voltage ( C – V ) and the leakage current density–voltage ( J – V ) characteristics. And the leakage current conduction mechanisms as functions of annealing temperatures are also discussed.