Novel pure-metal tri-axis CMOS-MEMS accelerometer design and implementation

This work proposed a pure-metal, single-proof-mass structure fabricated by the standard 0.18 mu m one-poly-silicon six-metal (1P6M) CMOS process along with one in-house post-CMOS wet-etching approach. The implemented state-of-the-art symmetrical tri-axis accelerometer consists of the disk-like mezzanine proof-mass and four diagonal double-layered springs. Three sets of the addressable quadrant electrodes underneath the proof-mass with additional interlayer inter-digital comb-conductors help to fulfil the high sensibilities of 248.6, 250.8, and 220.1 mV/G for the x-, y-, and z-axes, respectively. Symmetrical-structure and addressable-electrode design of the device also effectively eliminates the cross-coupling effects. The thin-film composite springs can be width-trimmed for the necessities of specification changes, and the optional calibration pads also provide the on-chip accuracy compensations. The fabricated tri-axis accelerometer reveals stable and consistent results and exemplifies a potential platform design for the highly integrated monolithic CMOS-MEMS system-on-chip applications.