Nature of chemical states of sulfur embedded in atomic-layer-deposited HfO2film on Ge substrate for interface passivation

Abstract

Sulfur was embedded in atomic-layer-deposited (ALD) HfO2 films grown on Ge substrate by annealing under H2S gas before and after HfO2 ALD. The chemical states of sulfur in the film were examined by S K-edge X-ray absorption spectroscopy. It was revealed that the valences of S-ions were mostly –2 at Ge/HfO2 interface (GeSx or HfO2–ySy to passivate the interface), while they were mostly +6 in HfO2 layers (sulfates; HfO2–z(SO4)z). The leakage current density in post-deposi-tion-treated film was lower than that in pre-deposition-treated one. This suggests that the passivation of defects in oxide layer by sulfate ions is more effective to lower the leakage current rather than the interface defect passivation by S2– ions. (© 2015 WILEY-VCH Verlag GmbH &Co. KGaA, Weinheim)