The impact of Hf metal pre-deposition on the physical and electrical properties of ultrathin HfO₂ films on Si_0.9954C _0.0046/Si heterolayers

The impact of Hf metal prior to the deposition of HfO₂ films on tensile-strained SiC layers is demonstrated. The physical thicknesses are found to be ∼4.5 nm and ∼3.5 nm for HfO₂/Hf gate stacks and HfO₂ films, respectively, by a high-resolution transmission electron microscope. The formation of a Hf-silicate layer due to Si diffusion into the high-κ films is confirmed by x-ray photoelectron spectroscopy measurements. The effective dielectric constants of κ ∼ 6 for HfO ₂ films and κ ∼ 13 for HfO₂/Hf gate stacks are calculated from the accumulation capacitance at the gate voltage of -2 V. The low leakage current density of ∼1 × 10^-4 A cm^-2 at -2 V, moderate interface state density of ∼1 × 10¹² cm^-2 eV^-1 and low capacitance equivalent thickness (CET) of ∼1.4 nm for HfO₂/Hf gate stacks on tensile-strained Si _0.9954C_0.0046 layers show a promising candidate for the new generation of complementary metal-oxide-semiconductor applications.