Composition dependent interfacial thermal stability, band alignment and electrical properties of Hf1−xTixO2/Si gate stacks

The optical properties, interface chemistry and band alignment of Hf1−xTixO2 (x = 0.03, 0.08, 0.12 and 0.20) high-k gate dielectric thin films, deposited by RF sputtering on Si substrate, have been systematically investigated. The effect of TiO2 incorporation on the interfacial chemical structure and energy-band discontinuities has been investigated by using X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible spectroscopy (UV-vis). It has been found that the band gap and band offsets of the Hf1−xTixO2 thin film decrease with the increase of TiO2 concentration. Meanwhile, the obtained band offsets are all over 1 eV. Thin film capacitors fabricated with the MOS configuration of Al/Hf1−xTixO2/n-Si/Al exhibits excellent electrical properties with low interface state density, hysteresis voltage and low leakage current density. The suitable band gap, symmetrical band offsets relative to Si and prominent electrical properties render sputtering-derived Hf1−xTixO2 with 9% TiO2 films as promising candidates for high-k gate dielectrics.