Silicon-based fluxgate magnetic sensors for weak magnetic field detection are investigated. A permalloy film is deposited and formed in the post processing. Metalization process is used for the excitation and pickup coils. The signal component is extracted by means of fluxgate principle together with the delta-sigma modulation to obtain high-precision digital output. The sensor chip shown below has been developed in collaboration with Swiss Federal Institute of Technology (ETH, Zurich) and was presented at ISSCC 1999. A weak magnetic field (Earth's magnetic field) is successfully measured as shown below.
|Magnetic sensor chip
|Response to weak magnetic field