Electrical properties of HfO2/La2O3 gate dielectrics on Ge with ultrathin nitride interfacial layer formed by in situ N2/H2/Ar radical pretreatment

In situ N2/H2/Ar radical pretreatment on p-type Ge (100) with HfO2/La2O3 high-κ gate oxide was investigated by remote rf plasma on radical-assisted atomic layer deposition. The interfacial LaGeOxNy formation and Ge outdiffusion were also investigated by x-ray photoelectron spectroscopy and transmission electron microscopy. The high-κ MOS device with an ultrathin LaGeOxNy interfacial layer shows good electrical characteristics, including larger κ value, smaller equivalent oxide thickness, lower leakage current density, smaller C-V hysteresis, and lower interface-state density. The involved mechanism lies in that the LaGeOxNy interfacial layer can effectively block Ge outdiffusion, thus improving the high-κ films/Ge interface quality.