Thin film packaging process for MEMS device using polycrystalline diamond

This work reports two designs of a poly-C thin film packaging process, each including an encapsulated poly-C device. The 1^st design uses boron-doped poly-C as electrical feedthroughs which can be embedded into the undoped, electrically insulating poly-C package. Access ports were opened along the package edge to release the thin film package and the device. Then, additional poly-C growth was used to seal the access ports. The 2^nd design is based on the concept of using porous diamond to release the structures from the top of the package, thereby significantly reducing the release and sealing time of the package, without significantly affecting the device. A preliminary test regarding the package´s fluidic hermeticity was performed to demonstrate that the poly-C thin film package has good fluidic hermeticity in an acidic environment. This is the first time that porous diamond created by RIE has been used in all-diamond thin film packaging including poly-C electrical feedthroughs, and a poly-C encapsulated device has been reported.