Structural and electrical properties of HfLaO_x films for an amorphous high-k gate insulator

Thin HfLaO_x films on Si(100) have been investigated as an alternative gate insulator. The introduction of La₂O₃ into HfO₂ causes an increase of crystallization temperature. Furthermore, unlike other Hf-based amorphous materials such as HfSiO_x or HfAlO_x, the permittivity of HfLaO_x keeps a high value (>20). The capacitance-voltage curve of metal oxide semiconductor capacitor using the HfLaO_x dielectric film has shown a negligible hysteresis and no frequency dispersion, indicating very small degradations of both interface and bulk properties. In addition, a very low fixed charge density in HfLaO_x films is demonstrated from a very small film thickness dependence of the flatband voltage.