Fully encapsulated sub-millimeter accelerometers

In this paper we present design, fabrication, and characterization results for the smallest published fully-packaged accelerometers. The miniaturization is realized by utilizing an advanced packaging scheme using a thick film epitaxial grown polysilicon encapsulation technique. Using this approach, released, encapsulated MEMS devices can be fabricated with exterior dimensions only 10s of microns larger than the micromechanical element. This advantage enables us to make accelerometers almost 2 orders of magnitude smaller than others. We have fabricated accelerometers as small as 0.034mm³ (387×387×230μm) with noise floor of 0.25mg/sqrt(Hz).