Thin-Film MOSFET-Based Pressure Sensor

This article proposes a silicon-on-insulator complementary metal-oxide semiconductor (CMOS) micro-electromechanical system (MEMS) thin-film pressure sensor in which the sensing elements are based on stress-sensitive MOSFETs, and the carrier mobility and channel resistance vary with applied pressure. Four MOSFETs are embedded within a silicon dioxide membrane to form a Wheatstone bridge. The sensors are fabricated in a commercial foundry with p-channel and n-channel designs both investigated. The fabricated pMOSFET design gave a pressure sensitivity of 5.21 mV/kPa, whereas the nMOSFET gave about half the sensitivity at 2.40 mV/kPa. This shows a highly sensitive pressure sensor, with improved sensitivity on traditional piezoresistors, as well as significantly higher sensitivity than current MOSFET based pressure sensors. Moreover, the maximum dc power consumption was only 190 and 390 mu W for the pMOSFET and nMOSFET, respectively. This low-cost, low-power, high-sensitivity CMOS MEMS technology with on-chip electronics could be used toward the implementation of MOSFET-based pressure transduction in a multitude of industrial and other applications.