Under pressure? Don’t lose direction! Smart sensors: Development of CMOS and MEMS on the same platform

Abstract

Micro Electro Mechanical Systems (MEMS) are movable structures fabricated on the surface of silicon chips by selectively depositing and etching away materials and silicon. Such movement allows the measurement of a wide range of parameters. In the recent years, the integration of MEMS devices and electronics on the same chip i.e. CMOS-MEMS integration, has allowed the improvement of sensors’ performance and fabrication costs, extending their integration in all types of devices. In the Advanced Hardware Architectures research group at the UPC, we are currently conducting research on system-on-chip CMOS-MEMS magnetic field and pressure sensors. Contrary to pressure sensors using other technologies, resonant pressure sensors allow direct coupling to digital electronics without requiring analog to digital converters (ADCs). This feature enhances their resolution and reliability by providing more immunity to noise and interference. Recently, monolithically integrated CMOS-MEMS resonant pressure sensors have been extensively used in atmospheric pressure monitoring and altitude sensing due to their low cost, small size and high reliability. Presently, the pressure sensors integrated in the smartphones and wearable devices suffer from poor sensitivity. The primary purpose of our study is to develop an optimized CMOS-MEMS resonant pressure sensor with enhanced sensitivity at atmospheric pressure which can be utilized in a vertical GPS enhancement system. Magnetic field sensors are key in the development of electronic compasses integrated in smartphones and other devices. Currently, magnetic sensors used in smartphones do not use MEMS technology but sensors that require materials incompatible with the fabrication of CMOS electronics. Our objective is to improve the performance of MEMS based electronic compasses by using Lorentz force based MEMS magnetic sensors. Such sensors, are compatible with CMOS process and could substitute actual sensors by reducing fabrication cost.