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 degrees 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 degrees C was estimated to be 9.20 x 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 x 10(-3) g m(-2) d(-1), the detection limit of the MOCON instrument used.