Improved electrical properties of Ge metal-oxide-semiconductor capacitor with HfTa-based gate dielectric by using TaOxNy interlayer

HfTa-based oxide and oxynitride with or without TaOxNy interlayer are fabricated on Ge substrate to form metal-oxide-semiconductor (MOS) capacitors. Their electrical properties and reliabilities are measured and compared. The results show that the MOS capacitor with a gate stack of HfTa-based oxynitride and thin TaOxNy interlayer exhibits low interface-state/oxide-charge densities, low gate leakage, small hysteresis, small capacitance equivalent thickness (∼0.94nm), and high dielectric constant (∼24). All these should be attributed to the blocking role of the TaOxNy interlayer against penetration of O into the Ge substrate and interdiffusions of Hf, Ge, and Ta, thus effectively suppressing the formation of unstable low-k GeOx and giving a superior TaOxNy∕Ge interface. Moreover, incorporation of N into both the interlayer and high-k dielectric greatly improves device reliability through the formation of strong N-related bonds.