Study of ZrO2 thin films for gate oxide applications

We investigated the microstructures and electrical properties of ZrO2 films deposited by reactive dc magnetron sputtering on Si substrates for gate dielectrics applications. We observed that the refractive index value of the ZrO2 films increased with an increase in deposition powers and annealing temperatures. The ZrO2 films deposited at elevated temperatures are polycrystalline, and both the monoclinic and tetragonal phases exist in the films. Films with higher density and improved crystallinity are obtained at higher deposition temperatures. The interfacial oxide layer between ZrO2 films and Si substrates grew upon annealing in the O2 gas ambient, which is due to the oxidation of Si substrates by the diffusion of oxidizing species from O2 gas ambient. The accumulation capacitance value increased upon annealing in the N2 gas ambient due to the densification of the films, while it decreased in O2 gas ambient due to the growth of the interfacial oxide layer.