Mixed Al and Si doping in ferroelectric HfO₂ thin films

Ferroelectric HfO₂ thin films 10 nm thick are simultaneously doped with Al and Si. The arrangement of the Al and Si dopant layers within the HfO₂ greatly influences the resulting ferroelectric properties of the polycrystalline thin films. Optimizing the order of the Si and Al dopant layers led to a remanent polarization of ∼20 μC/cm² and a coercive field strength of ∼1.2 MV/cm. Post-metallization anneal temperatures from 700 °C to 900 °C were used to crystallize the Al and Si doped HfO₂ thin films. Grazing incidence x-ray diffraction detected differences in peak broadening between the mixed Al and Si doped HfO₂ thin films, indicating that strain may influence the formation of the ferroelectric phase with variations in the dopant layering. Endurance characteristics show that the mixed Al and Si doped HfO₂ thin films exhibit a remanent polarization greater than 15 μC/cm² up to 10⁸ cycles.