Thin films of zirconium-doped tantalum oxide ͑Zr-doped TaO x ) deposited by reactive sputtering were studied in an effort to replace silicon dioxide (SiO 2 ) as the gate dielectric material for future metal-oxide-semiconductor devices. Influences of process parameters, such as Zr concentration, postdeposition annealing temperature, and film thickness, on the film's electrical and physical characteristics were investigated. The lightly Zr-doped film ͑15 nm thick͒ showed a low current density, e.g., 1.27 ϫ 10 Ϫ9 A/cm 2 at Ϫ1 MV/cm in the accumulation regime. The current conduction mechanism of the Zr-doped TaO x films was analyzed and compared with mechanisms of Poole-Frenkel and Schottky emissions. In comparison with pure tantalum oxide (TaO x ) and zirconium oxide (ZrO y ) films, the Zr-doped TaO x films had higher dielectric constants. A high-temperature annealing step reduced the film's hysteresis and fixed charge density. The interface layer composition changed from SiO x to zirconium silicate (Zr x Si y O) when the Zr concentration in the film was increased. The binding energies of Ta 4f, Zr 3d, and O 1s of the bulk shifted to lower values as the Zr concentration increased due to the charge transfer among elements. In summary, the Zr-doped TaO x films showed many advantages over pure TaO x and ZrO y films for the gate dielectric application.

Physical and electrical properties of hafnium-doped tantalum oxide thin films were studied. The doping process affects the structures, composition, thickness, dielectric constant, charges, and leakage current density of both the bulk film and the interface layer. Compared with the undoped film, the lightly doped film exhibited improved dielectric properties, such as a higher dielectric constant, a smaller fixed charge density, a larger dielectric strength, and a lower leakage current. The postdeposition annealing process condition, such as temperature and time, also influences the high-k film's dielectric properties. In summary, the hafniumdoped tantalum oxide film is a promising high-k gate dielectric material for future metal-oxide-semiconductor devices.

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