Miniature Planar Fluxgate Magnetic Sensors Using a Single Layer of Coils

The process complexity of a micromachined device is directly related to the number of layers needed. Miniature planar fluxgate magnetic sensors commonly use two or more layers of coils. The manufacture process of micromachined planar fluxgate sensors with all the coils contained in a single metal layer is here presented. The NiFe cores were electroplated through photoresist molds. Characterization in respect to noise levels and sensitivity are detailed discussed. Noise levels down to 40-nT rms in the 0.1-10 Hz range were achieved. Two different layouts are presented and one of them has the potential to further noise level reduction just by increasing either the excitation amplitude or the coils pitch.