PNNL

Abstract

Hafnium oxide (HfO2) thin films have been made by radio-frequency (rf) magnetron-sputtering onto Si(100) substrates under varying growth temperature (Ts). HfO2 ceramic target has been employed for sputtering while varying the Ts from room temperature to 500°C during deposition. The effect of Ts on the growth and microstructure of deposited HfO2 films has been studied using grazing incidence x-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HR-SEM) coupled with energy dispersive x-ray spectrometry (EDS). The results indicate that the effect of Ts is significant on the growth, surface and interface structure, morphology and chemical composition of the HfO2 films. Structural characterization indicates that the HfO2 films grown at Ts200 °C are nanocrystalline. An amorphous-to-crystalline transition occurs at Ts=200 °C. Nanocrystalline HfO2 films crystallized in a monoclinic structure with a (-111) orientation. XPS measurements indicated the high surface-chemical quality and stoichiometric nature of the grown HfO2 films. An interface layer (IL) formation occurs due to reaction at the HfO2-Si interface for HfO2 films deposited at Ts>200 °C. The thickness of IL increases with increasing Ts. XPS and EDS at the HfO2-Si cross-section indicate the IL is a (Hf, Si)-O compound. The electrical characterization using capacitance-voltage measurements indicate that the dielectric constant decreases from 25 to 16 with increasing Ts.