Characterization of Al incorporation into HfO₂ dielectric by atomic layer deposition

This study presents the characteristics of HfAlO films for a series of Al incorporation ratios into a HfO₂ dielectric by atomic layer deposition on a Si substrate. A small amount of Al doping into the HfO₂ film can stabilize the tetragonal phase of the HfO₂, which helps to achieve a higher dielectric constant (k) and lower leakage current density, as well as a higher breakdown voltage than HfO₂ film on its own. Moreover, assimilation of Al₂O₃ into HfO₂ can reduce the hysteresis width and frequency dispersion. These are indications of border trap reduction, which was also verified by the border trap extraction mechanism. X-ray photoelectron spectroscopy (XPS) analysis also verified the HfAlO microstructural properties for various Al compositions. In addition, higher amounts of Al₂O₃ in HfAlO resulted in better interface and dielectric behavior through trap minimization, although the equivalent-oxide-thickness (EOT) values show the opposite trend.