Wafer level vacuum encapsulated tri-axial accelerometer with low cross-axis sensitivity in a commercial MEMS Process

Abstract We present the design, fabrication and testing of a novel integrated tri-axial capacitive accelerometer with low cross-axis sensitivity. The accelerometer is fabricated in MEMS Integrated Design for Inertial Sensors (MIDIS), a process recently introduced by Teledyne DALSA Semiconductor Inc. (TDSI). The MIDIS process is based on high aspect ratio bulk micromachining of single-crystal silicon wafer that is vacuum encapsulated between two other silicon wafers. The fabrication process includes Through Silicon Vias (TSVs) with sealed anchors for compact flip–chip integration with microelectronic signal processing circuitry. The proposed accelerometer is designed to provide simultaneous detection of the input accelerations along the 3 principle axes enabling high-g measurement up to ±50 g. The integrated structure design uses decoupled frames supported by strategically designed springs and employs capacitive compensators for the purpose of achieving low cross-axis sensitivity. The capacitive transduction is based on differential measurement along X- and Y- axis and absolute measurement along the Z-axis. The initial measured capacitances are 2.18 pF, 2.4 pF and 1.14 pF along X, Y and Z-axis, respectively. The dynamic specifications of the accelerometer are characterized by its lowest-order operating mode at 4 kHz.