High quality interfacial sulfur passivation via H2S pre-deposition annealing for an atomic-layer-deposited HfO2 film on a Ge substrate

The effects of sulfur passivation of the Ge substrate were studied through (NH4)(2)S solution treatment and the rapid thermal annealing under an H2S atmosphere prior to atomic-layer-deposition (ALD) of HfO2. While a chemically unstable and uneven sulfur layer was formed by (NH4)(2)S solution treatment, a stable, highly uniform and dense sulfur layer with a thickness of similar to 2 nm was formed by H2S annealing on Ge substrates. The sulfur concentration at the interface increased with H2S annealing temperature. Sulfur passivation suppressed the diffusion of Ge into the HfO2 film and any interfacial layer growth during ALD, which resulted in a decreased equivalent oxide thickness of gate insulator. The interface properties, such as interface defect state density and hysteresis in capacitance-voltage behavior, were also improved by sulfur passivation through H2S annealing. H2S annealing is much more compatible with a mass-production process compared to the conventional (NH4)(2)S solution treatment process.