Thermal Stability of Atomic Layer Deposited Zr:Al Mixed Oxide Thin Films: An in Situ Transmission Electron Microscopy Study

The thermal stability of amorphous Zr:Al mixed oxide films of different composition, produced on (001) silicon wafers by the atomic layer deposition method is studied by transmission electron microscopy during in situ heating experiments. The temperatures at which phase separation and crystallization occur are composition dependent. The crystallization of thick films (55–70 nm), deposited on HF-treated silicon surfaces covered with a 15 cycles Al2O3 layer, results in the formation of cubic ZrO2 and cubic γ–Al2O3. In very thin films (5 nm), deposited on silicon surfaces covered with a 0.5 nm SiO2 thin film, the formation of tetragonal zirconium disilicide (ZrSi2) is observed in the microscope vacuum, at temperatures above 900 °C. This effect depends on the thickness of the as deposited thin film.