Metal-organic thin-film encapsulation for MEMS

This paper demonstrates a metal-organic thin-film encapsulation technique based on the photolithography of multiple layers of positive-tone photo-definable polymer. This encapsulation process, performed at low temperatures (<110 ◦C) in a standard basic developer, leaves no residue. Piezoelectrically-actuated length-extensional bulk acoustic wave resonators were successfully encapsulated for a proof-of-concept demonstration. Blanket metallization can lead to complete sealing, which helps exclude moisture and particles from sensitive MEMS devices such as high frequency resonators, RF filters and inertial transducers. (Some figures in this article are in colour only in the electronic version)