Dielectric properties of ultrathin hafnium oxide reoxidized with rapid thermal annealing (RTA) have been investigated. Capacitance equivalent oxide thickness (CET) of 45 Å hafnium oxide was scaled down to ∼10 Å with a leakage current less than 3×10−2 A/cm2 at −1.5 V (i.e., ∼2 V below VFB). Leakage current increase due to crystallization was not observed even after 900 °C rapid thermal annealing (RTA), but CET did increase after high temperature RTA due to the interfacial layer growth and possible silicate formation in the HfO2 film.

Hafnium oxynitride (HfOxNy) gate dielectric was prepared using reactive sputtering followed by postdeposition annealing at 650 °C in a N2 ambient. Nitrogen incorporation in the dielectric was confirmed by x-ray photoelectron spectroscopy analysis. In comparison to HfO2 of the same physical thickness, HfOxNy gate dielectric showed lower equivalent oxide thickness (EOT) and lower leakage density (J). Even after a high-temperature postmetal anneal at 950 °C, an EOT of 9.6 Å with J of 0.8 mA/cm2 @−1.5 V was obtained. In contrast, J of ∼20 mA/cm2 @−1.5 V for HfO2 with an EOT of 10 Å was observed. The lower leakage current and superior thermal stability of HfOxNy can be attributed to the formation of silicon–nitrogen bonds at the gate dielectric/Si interface and strengthened immunity to oxygen diffusion by the incorporated nitrogen.

The composition and atomic depth distributions of ultrathin zirconia films (ϳ30 Å ) deposited on Si͑100͒ have been investigated using medium-energy ion scattering ͑MEIS͒. Reoxidation in 18 O 2 permits the oxygen incorporation, exchange, and mobility to be followed due to the isotope sensitivity of the MEIS technique. These quantitative studies showed that significant interfacial SiO 2 growth results when reoxidizing samples at temperatures as low as 500°C, and that this growth saturates in time and pressure but increases with temperature. Substantial isotope exchange was also observed under various experimental conditions. The results are discussed taking into account published data on the bulk and grain boundary diffusion of O in monoclinic and tetragonal zirconia, the diffusivity of O in SiO 2 , and the nanocrystallinity of the films.

ZrO 2 thin film has been studied as an alternative gate dielectric. It was deposited directly on a Si substrate by reactive sputtering. An equivalent oxide thickness of less than 11 Å with a leakage current of 1.9×10−3 A/cm2 at −1.5 V relative to the flat band voltage has been obtained. Well-behaved capacitance–voltage characteristics with an interface state density of less than 1011 cm−2 eV−1 and no significant frequency dispersion have been achieved. Excellent reliability properties (e.g., low charge trapping rate, good time-dependent dielectric breakdown, low stress-induced leakage current, and high dielectric breakdown) have also been obtained.

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