Improved properties of Ge MOS capacitors with HfTiON or HfTiO gate dielectric by using Wet-NO Ge-surface pretreatment

HfTiO/GeO_xN_y and HfTiOn/GeO_xN_y stack gate dielectric are prepared by using wet-NO or wet-N₂O pretreatment on Ge substrate. Experimental results show that the wet NO pretreatment can lead to excellent interface properties, gate leakage properties and device reliability, especially for the HfTiON/GeO_xN_y dielectric. The involvement mechanisms lie in the roles of N in blocking oxygen diffusion and Ge out-diffusion and suitable N incorporation in the GeO_xN_y interlayer, which effectively suppress further growth of GeO_xN_y interlayer and the growth of unstable GeO_x during subsequent processing.