A MEMS sandwich differential capacitive silicon-on-insulator accelerometer

A differential capacitive accelerometer with simple process is designed, simulated, and fabricated. To achieve a precision structure dimension with fewer processing steps, the silicon device layer transfer technology is being used to built a sandwich accelerometer based on a silicon-on-insulator (SOI) wafer, which was assembled by glass-si-glass multilayer anodic bonding. Deep reactive ion etching is being used to define symmetric beams and large mass block of equal thickness together in SOI device layer (up to 100 μm) in a single step to avoid alignment error in double side process. An actual accelerometer which is designed for 50 g measure range is fabricated with six lithography steps. Measurement results show 0.1166 V/g sensitivity and 0.022 % nonlinearity error in ±1 g gravity static response test. The accelerometer also provides a power spectrum less than 10.49 μVrms/Hz1/2 (89.97 μg/Hz1/2) in a non-isolated laboratory environment with a capacitive interface circuit.