Wafer-Level Encapsulation and Sealing of Electrostatic HARPSS Transducers

This paper reports on a thin-film wafer-level encapsulation technique for packaging and CMOS integration of MEMS sensors and actuators fabricated through the HARPSS process. This approach takes advantage of the stationary parts of the micromechanical device itself for encapsulation of its sensitive moving parts, and therefore can be performed without addition of extensive processing steps. Encapsulated high frequency capacitive silicon resonators are demonstrated using this technique. Reliability and performance tests conducted on the encapsulated resonators reveal a high level of hermeticity and reliability with minimal interference with device operation. This technique can be applied to a wide variety MEMS sensors and actuators. Silicon transducers encapsulated using this approach can run through the regular IC fabrication and/or packaging processes.