UV assisted oxidation and nitridation of hafnia based thin films for alternate gate dielectric applications

The synergistic effects of NH3 ambient and ultraviolet illumination on the dielectric properties of hafnia based gate dielectrics are reported in this paper. The films were processed at relatively low temperatures (∼400 °C) by pulsed laser ablation and UV oxidation technique. UV illumination and the NH3 ambient created a thin and a denser interfacial layer (at the film-Si interface) comprised of HfSiON bonding. As a result of the interfacial layer modification, a leakage current density lower than 10−4 A/cm2 and a dielectric constant of ∼21.7 were extracted from the best samples processed in NH3 and under UV illumination. The nitrogen doped HfO2 also exhibited a thinner interfacial layer (∼12 Å) in comparison to the films processed without NH3 ambient.