Thin film encapsulation by e-beam evaporation of oxides

A few oxide thin films, SiO₂, TiO₂, Al₂O₃ and ZrO₂ were deposited by e-beam evaporation and evaluated on their encapsulation performance. Ca buttons were used as sensors to detect the permeated oxygen and moisture through the oxide barrier layers. The metal Ca sensors coated by the barrier layers were microscopically observed. The results showed that the optimal single layer thickness was varied from 10 to 50 nm, depending on the oxide material. A thicker layer than 60 nm was not helpful for improvement of barrier performance, likely due to the existence of imperfects on substrate and the creation of cracks due to the large residual stress of the oxide thin films. As thin film encapsulation materials, e-beam evaporated Al₂O₃ and ZrO₂ are superior to SiO₂ and TiO₂ in barrier performance.