Development of multi-axes CMOS-MEMS resonant magnetic sensor using Lorentz and electromagnetic forces

The stacking of metal/tungsten layers as the in-plane magnetic-coil for CMOS-MEMS magnetic sensor has been proposed and demonstrated for the first time. Magnetic fields introduce forces through in-plane coils to drive suspended spring-mass structure. Capacitance sensing electrodes could detect the dynamic response of spring-mass structure to determine magnetic fields. Such design has the following advantages: (1) Number of turns for proposed in-plane magnetic-coil is not restricted by the space and thin film layers, (2) in-plane magnetic-coil could respectively generate Lorentz and electromagnetic forces by out-of-plane and in-plane magnetic fields for multi-axes magnetic field detection, and (3) easy integration with CMOS-MEMS accelerometers and sensing circuits [1]. The design was implemented using the standard TSMC 2P4M CMOS process. A 400μm×300μm proof-mass with embedded in-plane magnetic-coil of 35-turns/5μm-wide is demonstrated. Measurement indicates the 3-axis magnetic fields were successfully detected using two monolithically integrated perpendicular sensing units. At 1atm, the sensor has the resolution of 319.9nT/rtHz (x-axis magnetic field), 296.5nT/rtHz (y-axis), and 121.6nT/rtHz (z-axis).