CMOS 3‐D‐Integrated MEMS Sensor

This chapter presents one TSV‐less 3‐D complimentary metal‐oxide semiconductor (CMOS)‐on‐micro‐electro‐mechanical system (MEMS) integration technique using direct metal bonding. The CMOS‐on‐MEMS integration leads to a simultaneous formation of electrical, mechanical, and hermetic bonds, eliminates chip‐to‐chip wire‐bonding, and hence presents competitive advantages over hybrid or monolithic solutions. The MEMS sensor is a capacitive accelerometer. The basic working principle of the MEMS accelerometer is the displacement of a small proof mass etched into the silicon surface of the integrated circuit and suspended by small beams. The CMOS readout circuit for MEMS consists of a low‐noise, band‐pass gain stage, a fully differential synchronous demodulator, and an off‐chip, low‐pass filter. The chapter illustrates a figure of the heterogeneous 3‐D TSV‐less accelerometer structure. The CMOS readout circuit is stacked on the MEMS accelerometer using face‐to‐face (F2F) direct metal bonding, which provides smaller form factor, latency, and power.