Interface and electrical properties of ultra-thin HfO2 film grown by radio frequency sputtering

Interfacial composition and electrical properties of ultra-thin hafnium oxide (HfO2) films on p-type <100> Si substrate are reported. Hafnium oxide (HfO2) thin films are prepared using radio-frequency sputtering method and subsequently annealed at different temperature. The effect of post-deposition annealing on the interfacial and chemical state of HfO2/Si gate stack has been characterised by means of X-ray reflectivity and X-ray photoelectron spectroscopy studies. Peaks of X-ray photoelectron spectroscopy spectra at 530.50 and 532.25 eV originate from Hf–O–Si bond illustrated the creation of Hf-silicate based interfacial layer at the high-k/Si interface. X-ray reflectivity fitting result also corroborated the formation of Hf silicate interfacial layer. Capacitance-voltage measurements revealed insignificant hysteresis in case of film annealed at 600 °C. Interface trap density has been extracted using Terman method and is found to be 3.18×10−11 cm−2 eV−1 at −1.0 V. Minimum equivalent oxide thickness (EOT) of 1.3 nm was obtained for the film annealed at 600° C. The gate leakage current density of the HfO2 film annealed at 600 °C is 1.5×10−5 A/cm2 at a bias voltage of −2 V.