Oxidation of sputtered Zr thin film on Si substrate

Abstract

Oxidation of sputtered Zr thin film on Si substrate has been investigated by varying oxidation times (5–60 min) at 500 °C. Fourier transform infrared spectroscopy indicated the existence of ZrO2 by showing spectra of Zr–O. Vibration mode of Si–O and Zr–O–Si are also detected for all samples oxidized at different duration. This suggested the existence of SiO x and Zr x Si y O z compounds and they might be located at interfacial layers (ILs) between ZrO2 and Si. Cross-sectional image of high resolution transmission electron microscopy taken from 60-min oxidized sample showed that both ZrO2 and IL thickness is ~3.5 nm. Time-of-flight secondary-ion-mass spectroscopy suggested that Zr x Si y O z may be formed after oxidized for 15 min. The proposed IL is consisted of a mixture of Zr x Si y O z and SiO x . A physical model has been established to explain the observation. Electrical characterization shows that capacitance–voltage curves have small hysteresis and their flatband voltages are shifted to a negative bias. Effective dielectric constant values of the investigated oxides are in the range of 4.22–5.29. Leakage current density–breakdown voltage characteristic shows that 5-min oxidized sample has the lowest dielectric breakdown voltage if compared with the other samples.