Investigation of the chemical state of ultrathin Hf–Al–O films during high temperature annealing

Abstract

Al 2O 3 incorporated HfO 2 films grown by atomic layer deposition (ALD) were investigated by high-resolution X-ray photoelectron spectroscopy (HRXPS). The core level energy state of a 15 Å thick film showed a shift to higher binding energy, as the result of a silicate formation and Al 2O 3 incorporation. The incorporation of Al 2O 3 into the HfO 2 film had no effect on silicate formation at the interface between the film and Si, while the ionic bonding characteristics and hybridization effects were enhanced compared to a pure HfO 2 film. The dissociation of the film in an ultrahigh vacuum (UHV) is effectively suppressed compared to a pure HfO 2 film, indicating an enhanced thermal stability of Hf–Al–O. Any dissociated Al 2O 3 on the film surface was completely removed into the vacuum by vacuum annealing treatment over 850 °C, while HfO 2 contributed to Hf silicide formation on the film surface.