Electrical and material characteristics of the sub 5 nm hafnium doped tantalum oxide high k film

Ultra-thin films (less than 5 nm) of hafnium doped tantalum oxide (Hf-doped TaO_x) high-k dielectric films were deposited by reactive sputtering as alternative gate dielectric materials for future CMOS devices. A film with an equivalent oxide thickness (EOT) of 13 Å and a leakage current density of 7×10^-3 A/cm² at -1 V relative to the flat-band voltage has been obtained. The Hf-doped TaO_x film is composed of HfO_x and TaO_x. The binding energy of Ta 4f in the film shifts to a lower value with the inclusion of the Hf in the film due to charge transfer among elements. The Hf-doped film remains amorphous after 700°C N₂ or O₂ annealing. The N₂ annealed film has a lower EOT, a thinner interfacial layer, and a higher leakage current than the O₂ annealed film.