Nature of chemical states of sulfur embedded in atomic-layer-deposited HfO2 film 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-deposition-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 S-2 ions. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim