Annealing temperature dependence on the structural and optical properties of sputtering-grown high-k HfO2 gate dielectrics

Abstract

High-k gate dielectric HfO2 thin films have been deposited on Si and quartz substrates by radio frequency magnetron sputtering. The structural characteristics, surface morphology, and optical properties of the HfO2/Si gate stacks at various post-annealing temperatures were examined by X-ray diffraction (XRD), atomic force microscopy (AFM), fourier transform infrared spectroscopy (FTIR), ultraviolet–visible spectroscopy (UV–Vis spectroscopy), and spectroscopic ellipsometry (SE). XRD measurement indicates that the 80 W-deposited HfO2 films demonstrate a polycrystalline structure. AFM measurements illustrate that the root mean square of the HfO2 thin films demonstrates an apparent increase with increasing the annealing temperature. Analysis from FTIR indicates that the Si–O–Si bonds vibration peak position shift toward lower wave numbers with increasing the annealing temperature. Combined with UV–Vis spectroscopy and SE measurements, it can be noted reduction in band gap with an increase in annealing temperature has been confirmed. Additionally, increase in refractive index (n) has been confirmed by SE.