Effects of Heating Time and Intermediate Heating on Sol–Gel-Processed ZrO₂ Thin Films

Nanoscale-thick high-k ZrO₂ films were fabricated via sol–gel method and the effects of heating time and an intermediate heat treatment on the microstructure and dielectric properties were studied. One set of films was spin-coated with a thickness of ∼13 nm on Si substrates by two consecutive coating and drying sequences, followed by heating at 500 °C for 1, 5, or 10 h, while another sample was prepared by heating at 500 °C for 1 h after each drying step (intermediate heated sample). As the heating time was extended, the permittivity increased, but the leakage current property degraded. In contrast, both the permittivity and leakage current property were enhanced in the case of the intermediate heated sample. These improvements were likely due to the effective elimination of remnant organics and the development of a two-layer morphology consisting of lower amorphous and upper crystalline layers, the formation of which occurred via the minimization of surface and strain energies.