UV-enhanced atomic layer deposition of Al2O3 thin films at low temperature for gas-diffusion barriers

Abstract

We present ultraviolet (UV) enhanced atomic layer deposition (ALD), UV-ALD, as a promising approach to deposit effective gas-diffusion barrier thin films. Highly dense, uniform, and conformal Al₂O₃ thin films were prepared by UV-ALD at 40 °C, suggesting that UV irradiation during the ALD process promotes the reactions to achieve an ideal ALD process even at low temperature. The water-diffusion barrier performance of the Al₂O₃ thin films was found to be significantly enhanced by the use of UV irradiation. The water vapor transmission rate of Al₂O₃ films grown by UV-ALD at 40 °C was estimated to be 9.20 × 10⁻⁷ g m⁻² d⁻¹ using a Ca conductance test, which is one of the lowest reported WVTR values among the ALD Al₂O₃ barrier thin films and satisfies the WVTR requirement of 10⁻⁶ g m⁻² d⁻¹. The WVTR measurements were also performed by MOCON testing using 10–100 nm thick Al₂O₃ thin films on PET substrates, also showing superior performance of the UV-ALD thin films to that of the thermal ALD film. All the UV-ALD films except the 10 nm-thick one show WVTR values below 1.00 × 10⁻³ g m⁻² d⁻¹, the detection limit of the MOCON instrument used.