Modulation of the microstructure, optical, and electrical properties of HfYO gate dielectrics by annealing temperature

Highlights: • Sputtering-derived HfYO gate dielectrics have been deposited on Si substrates. • Y incorporation leads to the increase of band gap energy and the reduction of refractive index. • Improved electrical performance can be attributed to the increased band gap and conduction band offset. In this study, Y-doped HfO₂ (HYO) high-k gate dielectric thin films have been deposited on cleaned n-type Si wafers by using co-sputtering technique. Annealing temperature dependent structural, optical, interfacial and electrical properties of HYO have been systemically studied using the x-ray diffraction (XRD), ultraviolet–visible spectroscope (UV–Vis), spectroscopy ellipsometry (SE), x-ray photoelectron spectroscopy (XPS) and electrical measurements. Based on XRD measurements, it can be noted that cubic phase has been detected and remained while doping with yttrium element and annealing at high temperature. Optical analysis by SE indicates that incorporation of Y into HfO₂ can enlarge the band gap and decrease the refraction index of the samples. High temperature annealing leads to the formation of low-k SiO₂ layer and silicate. Electrical measurements have demonstrated that MOS capacitor based on HYO/Si gate stack annealed at 400 °C shows excellent electrical properties, such as high dielectric constant, low oxide charge density border trapped oxide charge density and leakage current density, which can be attributed to the increase in band gap and conduction band offset by Y incorporation.