Dependence of ozone concentration on the moisture barrier properties of aluminum oxide using atomic layer deposition

Abstract

As a thin film encapsulation method, atomic layer deposition (ALD) has the potential to provide superior protection for organic light-emitting diodes (OLEDs). However, the application of H₂O and O₂ plasma in the traditional ALD process has not yet resulted in a successful moisture barrier. The large dipole moment of H₂O may result in excess residual hydroxyl groups, and the flux of charged particles from O₂ plasma can damage organic materials. Here, we suggest the use of ozone (O₃) as an alternative reactant to mitigate these limiting factors. It is a powerful oxidizer and is much more volatile than other oxidizing agents. Thus, O₃ is a promising oxygen source to improve moisture barrier properties for OLEDs. This work describes the dependence of O₃ concentration on the moisture barrier properties of Al₂O₃ thin films prepared by ozone-based ALD at 100 °C. Trimethylaluminum and O₃ were utilized as aluminum and oxygen precursors, respectively. The O₃ concentration varied from 100 to 400 g/m³ in increments of 100 g/m³. An increase in O₃ concentration resulted in a significant enhancement in the moisture barrier performance of Al₂O₃, with values improving from 7.1 × 10⁻⁴ to 1.9 × 10⁻⁵ g/m²/day. Further characterization indicated that Al₂O₃ thin films produced at elevated O₃ concentrations exhibited superior physical and chemical properties compared to those generated at lower O₃ concentrations.