Influences of annealing on structural and compositional properties of Al₂O₃ thin films grown on 4H-SiC by atomic layer deposition

Annealing effects on structural and compositional performances of Al₂O₃ thin films on 4H-SiC substrates are studied comprehensively. The Al₂O₃ films are grown by atomic layer deposition through using trimethylaluminum and H₂O as precursors at 300℃, and annealed at various temperatures in ambient N₂ for 1 min. The Al₂O₃ film transits from amorphous phase to crystalline phase as annealing temperature increases from 750℃ to 768℃. The refractive index increases with annealing temperature rising, which indicates that densification occurs during annealing. The densification and grain formation of the film upon annealing are due to crystallization which is relative with second-nearest-neighbor coordination variation according to the x-ray photoelectron spectroscopy (XPS). Although the binding energies of Al 2p and O 1s increase together during crystallization, separations between Al 2p and O 1s are identical between as-deposited and annealed sample, which suggests that the nearest-neighbour coordination is similar.