Dielectric characteristics of Al2O3–HfO2 nanolaminates on Si(100)

The structural characteristics and the chemical state of a ${\mathrm{HfO}}_2–{\mathrm{Al}}_2{\mathrm{O}}_3$ nanolaminate structure, depending on the postannealing temperature, were examined by x-ray diffraction and x-ray photoelectron spectroscopy. The structural stability is significantly enhanced up to 870 °C and so is able to sustain its amorphous and laminate structure. However, the laminate structure is drastically broken at the annealing temperature of 920 °C and the crystallization is locally generated. In particular, the formation of the interfacial layer during the postannealing treatment is effectively suppressed in the nanolaminated structure. The dielectric constant of the nanolaminate structure calculated from the accumulation capacitance increases from ∼10 to ∼17 as the annealing temperature increases. This change is closely related to the degree of the mixture composed by ${\mathrm{Al}}_2{\mathrm{O}}_3$ and ${\mathrm{HfO}}_2.$