Micro-G silicon accelerometer using surface electrodes

Abstract

We present a new technology platform for silicon inertial sensors. The platform combines three technology features to set new performance and manufacturability standards for MEMS sensors. First, bonding three silicon wafers creates wafer level packaging and a homogenous stack of silicon material improving device temperature stability. Second, through-wafer etching is used to define the mechanical structure creating a proof mass with 1000x larger mass than a typical MEMS sensor. Finally, we use surface electrode technology to create a lateral capacitance-based transducer enabling large capacitance change per acceleration and allowing a large dynamic range without electrode contact. The large mass together with reduced damping of a lateral sensor result in substantially reduced thermal-mechanical noise. We present a two axis, in-plane, MEMS accelerometer having nG/√Hz noise performance, over 130 dB dynamic range, 300 Hz bandwidth, and a chip size comparable to other MEMS accelerometers. The platform is extensible to gyroscopes and single chip IMU.