A novel suspension design for MEMS sensing device to eliminate planar spring constants mismatch

This paper presents a new suspension design for planar MEMS sensing devices. The new design includes four coil springs which are symmetrically arranged with respect to the center of the proof mass with 90-degree orientation difference. The proposed coil spring design is found to take less area to achieve similar spring constant than the conventional serpentine spring design. Furthermore, the proposed symmetrical-to-center arrangement on suspension can reduce spring constants mismatch between X and Y axes, even under beam width deviation due to fabrication resolution. This concept is realized and verified by experimental results from two-axis capacitive accelerometers through a polysilicon-based CMOS fabrication platform.