Effect of AcAc/Al molar ratio on morphological and electrical properties of spray-coated Al2O3 thin films

We present a spray pyrolysis method that can form amorphous Al2O3 thin films for dielectric applications using low-cost precursor materials. The effect of the precursor molar ratios on morphological and electrical properties of spray-coated Al2O3 thin films was studied. For a low molar ratio of acetylacetone (AcAc) to Al ions (AcAc/Al), inhomogeneous morphology with the formation of large particles was observed. The increase in AcAc/Al improves the coverage of Al by AcAc molecules, which prevents the premature solidification of Al ions, resulting in compact films with smooth surfaces. On the contrary, excessive AcAc for the high AcAc/Al leaves cracks in the films due to the evaporation of AcAc during film deposition. Electrical measurements on metal-insulator-metal (MIM) structures showed consistent results, and superior dielectric performance with sufficiently low leakage current was observed for the optimized AcAc/Al values.