Improved electrical properties of Ge metal-oxide-semiconductor capacitors with high-k HfO₂ gate dielectric by using La₂O₃ interlayer sputtered with/without N₂ ambient

The electrical properties of n-Ge metal-oxide-semiconductor (MOS) capacitors with HfO₂/LaON or HfO₂/La₂O₃ stacked gate dielectric (LaON or La₂O₃ as interlayer) are investigated. It is found that better electrical performances, including lower interface-state density, smaller gate leakage current, smaller capacitance equivalent thickness, larger k value, and negligible C-V frequency dispersion, can be achieved for the MOS device with LaON interlayer. The involved mechanism lies in that the LaON interlayer can effectively block the interdiffusions of Ge, O, and Hf, thus suppressing the growth of unstable GeO_x interlayer and improving the dielectric/Ge interface quality.