Monolithic Isotropic 3D Silicon Hall Sensor

This paper reports on a monolithic three-dimensional (3D) Hall sensor enabling to measure the three spatial components of the magnetic field with identical sensitivity. It is therefore the first technical realization of a Hall-effect-based sensor with isotropic response relying on a single volume of semiconducting material. The overall shape of the active volume is that of a regular hexagonal prism with parallel top and bottom bases. The sensor has only six contacts arranged as groups of three on the two base surfaces. Sending currents obliquely across the device allows one to operate it as three mutually crossing, identical, and effectively orthogonal Hall sensors. Full advantage can be taken of offset-cancellation techniques such as current spinning. In this study, design variants are evaluated with the focus in particular on the isotropy of the three sensitive directions and the minimization of the initial offset voltages. We demonstrate a design in silicon technology which has pairwise orthogonal sensitivity vectors with magnitudes of 34.4±0.2 mV/VT and shows initial offset values of about 2 mV at an input current of 3.5 mA, corresponding to a drive voltage of 1 V. After current spinning the equivalent magnetic offset is reduced to 29 μT. The extraction of 3D magnetic fields with angular and magnitude uncertainties of 0.3° and 0.5% is demonstrated.