A 400×400µm2 3-axis CMOS-MEMS accelerometer with vertically integrated fully-differential sensing electrodes

This study presents a novel CMOS-MEMS 3-axis accelerometer design using TSMC 0.18μm 1P6M CMOS process. Thus, the footprint size of 3-axis accelerometer is significantly reduced to 400×400μm² by the single proof-mass design, Due to the novel fully-differential gap-closing sensing electrode design in all three sensing directions, the sensitivities of 3-axis accelerometer are improved. Moreover, by means of metal wet-etching post-CMOS process, very small in-plane and out-of-plane sensing gaps are respectively defined by the minimum line width and one metal-layer thickness of TSMC process. Thus, the sensitivity of accelerometer is further improved. Table1 summarize the measured performances of proposed accelerometer, which indicates its chip size and performances are better than existing designs.