Study of interfacial reactions and phase stabilization of mixed Sc, Dy, Hf high-k oxides by attenuated total reflectance infrared spectroscopy

Grazing angle attenuated total reflectance Fourier transform infrared spectroscopy is applied to study ultrathin film Hf4+, Sc3+ and Dy3+oxides, due to its high surface sensitivity. The (multi)metal oxides studied, are of interest as high-k dielectrics. Important properties affecting the permittivity, such as the amorphous or crystalline phase and interfacial reactions, are characterized. Dy2O3 is prone to silicate formation on SiO2/Si substrates, which is expressed in DyScO3 as well, but suppressed in HfDyOx. Sc2O3, HfScOx and HfO2 were found to be stable in contact with SiO2/Si. Deposition of HfO2 in between Dy2O3 or DyScO3 and SiO2, prevents silicate formation, showing a buffer-like behavior for the HfO2. Doping of HfO2 with Dy or Sc prevents monoclinic phase crystallization. Instead, a cubic phase is obtained, which allows a higher permittivity of the films. The phase remains stable after anneal at high temperature.