Advanced atmospheric-pressure spatial atomic layer deposition for OLED encapsulation: Controlling growth dynamics for superior film performance

Abstract

The next-generation display industry, based on organic light-emitting diodes, requires high-performance thin-film encapsulation layers (TFEs) to resist ambient moisture and hydrogen. Atomic layer deposition (ALD) is regarded as a suitable process for the fabrication of high-performance TFEs. However, ALD has the drawback of long processing times. This limitation can be overcome with spatial atomic layer deposition (S-ALD). In this study, we used S-ALD to deposit Al2O3 films for TFE, at a low processing temperature of 100 °C, to control process parameters for trimethyl-aluminum (TMA) exposure, i.e., the TMA partial pressure and substrate speed, defining four process conditions (A, B, C, and D) with similar growth per cycle (GPC) values. By analyzing the growth behavior of Al2O3 under each process condition based on the Langmuir adsorption model, we expressed the variations as differences in GPC. These differences in growth behavior led to variations in the physical and chemical properties of the Al2O3 films, impacting their water vapor transmission rate (WVTR) performance. Based on these differences, we combined process conditions A and D in situ to fabricate high-performance encapsulation Al2O3 films with a WVTR of 4.4 × 10−5 g/(m2 day) and H2 permeability of 1.7 × 10−4 barrer. This was achieved at atmospheric pressure (AP) with a high productivity rate of 37.44 Å/min. This research highlights that the growth behavior of Al2O3 in AP S-ALD can be controlled by adjusting the TMA partial pressure and substrate speed. By applying a hybrid process, we successfully developed high-performance encapsulation Al2O3 films with a high throughput.