Impact of annealing on electric and elastic properties of 10-nm Hf0.5Zr0.5O2 films prepared on Si by sputtering

HfO2-based films are important materials used in broad range of electronic applications from high-performance transistors and memory cells, to thermoelectric and energy harvesting elements. By employing scanning probe methods, we made nanoscale comparison of chemical composition, surface morphology, the elastic modulus and the surface potential of bare 10-nm thick Hf0.5Zr0.5O2 films prepared on Si by a carbon-free sputtering process. The composition mapping confirmed uniform distribution of Hf and Zr in the film along wafer size. Suppression of the monoclinic phase in films annealed at 600 - 800 °C had strong impact on spatial variations of film properties. Small surface roughness, large electric domain sizes (50–200 nm at 700 °C) and small fluctuations of the surface potential (40–50 meV) in Si coated with the films are appealing for gate-stack applications. Films annealed at 600-700 °C showed the elastic modulus of about 169 GPa and the ferroelectric polarization reversal at a field of ~1 MV/cm as observed by nanoscale poling with a Pt-coated scanning probe. In contrast, properties of films annealing at 800 °C were affected by growth of thick interfacial oxide layer. The presented nanoscale approach is beneficial in optimizing of physical and mechanical properties of thin dielectric films.