High-Q Lorentz force MEMS magnetometer with internal self-amplification

This work presents a MEMS resonant Lorentz force magnetometer with internal self-amplification using the thermal-piezoresistive quality factor (Q) enhancement effect in silicon microstructures. Close to three orders of magnitude (~720X) improvement in sensitivity of the sensor is demonstrated by increasing the resonator bias current from 1 mA to 28 mA. Magnetometer sensitivity figure-of-merit (FOM), defined as sensitivity (mV/T) over piezoresistor bias current, has increased from 1.3Ω/T (mV/Tesla/mA) to 36.3Ω/T by amplifying resonator Q from its intrinsic value of 494 to 13,571 in air. Further amplification up to 3-4 orders of magnitude sensitivity FOM and much higher sensitivities are expected to be achievable if narrower resonator actuator beams are used. Preliminary results on the presented magnetometer show sensitivities as high as 1.01V/T (minimum detectable field in the nT range) while operating in air.