Air-gap in encapsulation for fast release and safe sealing

Abstract

This paper reports an air-gap effect on fast release of the thin film encapsulation for packaging of MicroElectroMechanical System (MEMS) devices. The air-gap structure which is defined between the cap and sacrificial layer solves the main issue of longer release time in thin film encapsulation (TFE). Sacrificial layer could be removed very fast during release step because this air-gap provide large exposed sacrificial layer surface to etch. Furthermore, proper position of etch holes on the cap makes possible to protect the mass loading without any release delay. The effectiveness of our scheme is shown experimentally by reducing the release time for 26 μm × 26 μm size encapsulation by a factor 6 in comparison of sidewall located channel. Furthermore, theoretical calculation shows that the effectiveness of our scheme can increase dramatically for larger TFE. For example, 800 μm × 800 μm size of encapsulation with air-gap in encapsulation have been fully released in 1.8 minutes which is 100 times less than that of sidewall located channel scheme.