Foundry Service of CMOS MEMS Processes and the Case Study of the Flow Sensor

The complementary metal‐oxide‐semiconductor (CMOS) process is the main stream to fabricate integrated circuits (ICs) in the semiconductor industry. Microelectromechanical systems (MEMS), when combined with CMOS electronics to form the CMOS MEMS process, have the merits of small features, low power consumption, on‐chip circuitry, and high sensitivity to develop microsensors and micro actuators. Firstly, the authors review the educational CMOS MEMS foundry service provided by the Taiwan Semiconductor Research Institute (TSRI) allied with the United Microelectronics Corporation (UMC) and the Taiwan Semiconductor Manufacturing Company (TSMC). Taiwan’s foundry service of ICs is leading in the world. Secondly, the authors show the new flow sensor integrated with an instrumentation amplifier (IA) fabricated by the latest UMC 0.18 μm CMOS MEMS process as the case study. The new flow sensor adopted the self‐heating resistive-thermal‐detector (RTD) to sense the flow speed. This self‐heating RTD half‐bridge alone gives a normalized output sensitivity of 138 μV/V/(m/s)/mW only. After being integrated with an on‐chip amplifier gain of 20 dB, the overall sensitivity of the flow sensor was measured and substantially improved to 1388 μV/V/(m/s)/mW for the flow speed range of 0–5 m/s. Finally, the advantages of the CMOS MEMS flow sensors are justified and discussed by the testing results.