Thin-film encapsulation technology for above-IC MEMS wafer-level packaging.

This work presents a low-cost and low-temperature wafer-level packaging solution for microelectromechanical systems (MEMS) devices. Heat-sensitive polymer poly(propylene carbonate) is used as the sacrificial material to release the capping layer in a clean and fast manner. Free-standing caps made of amorphous silicon carbide films and as large as 450 µm in diameter are successfully fabricated. To demonstrate the validity of this technology, surface-micromachined Pirani vacuum gauges are fabricated as an example of MEMS devices and encapsulated. Capped Pirani gauges respond to pressure between 1 mTorr and 1 atm. The Pirani gauges are sealed with Parylene C films that exhibit near-hermetic properties and the initial sealing pressure for 300 µm diameter cavities is characterized to be in the range of tens of torr. [ABSTRACT FROM AUTHOR]