Thin films of (HfO2)x(Al2O3)1−x alloys: Preparation, chemical structure and dielectric properties

Thin films of (HfO₂)_x(Al₂O₃)_1-x alloys were prepared by chemical vapor deposition using the volatile coordination compounds. Amorphous structure of the films has been revealed by X-ray analysis when the Al content is of >30%. It was shown by EDS and XPS that Al concentration increases with rising the substrate temperature and content of the Al(acac)₃ in mixture of the precursors. Formation of (HfO₂)_x(Al₂O₃)_1-x alloys is rather than HfO₂ and Al₂O₃ mixture. Decreasing the Al concentration in the line from the interface to the films surface has been observed for the films deposited by using the source with the precursors mixture. The refraction index is the function of the chemical composition variations through the film thickness. The refractive index is invariant through the thickness for the layers deposited by using two spaced sources of the precursors. This is an indication of the uniform components distribution. As the dielectrics for the MIS-structures the (HfO₂)_x(Al₂O₃)_1-x thin films show the lower permittivity (k=11-16) than HfO₂ films (k=15 - 20), but the smaller leakage current to values of j = 10^-6 - 10^-8 A/cm².