Wafer-scale film encapsulation of micromachined accelerometers

Micromachined accelerometers have been one of the most successful MEMS devices. Once a successful MEMS device is developed, packaging is the most critical step commercializing the device. Micromachined accelerometers are currently packaged with a separate lid made of glass or silicon bonded on the accelerometer device wafer. In this study, we have developed a new advanced packaging scheme using a thick film epitaxial grown polysilicon encapsulation. With this method, we can reduce the total die size and reduce an additional "cap" wafer; both result in cost reduction. Furthermore the encapsulation can withstand conventional post processing, such as dicing, wire bonding and even injection molding. This paper will discuss the packaging process and show performance results from encapsulated piezoresistive and capacitive accelerometers.