A study on a silicon Hall effect device with an integrated electroplated planar coil for magnetic sensing applications

Hall effect devices have experienced extensive use, particularly for current sensing and power metering applications. Silicon Hall effect devices give low sensitivity compared to other materials such as InSb, owing to its relatively low electron and Hall mobilities. However, in identifying a relatively inexpensive solution in a planar format compatible with established processing techniques, silicon is ideal. In this work, the performance of an inexpensive silicon Hall effect device with an integrated planar coil is discussed for use in various applications such as power monitoring. The rectangular conventional Hall device was fabricated on n-type epitaxial silicon while the integrated planar coil was fabricated using electroplated copper. The choice of electroplated copper over a thin film evaporated metal was to enhance the current handling capability of the planar coil, thereby increasing the magnetic field generated. However, a limit to current exists as higher current levels heat the substrate, resulting in a drift in the Hall voltage. In an effort to confine the magnetic field, an electrolytically deposited Ni/Fe core was introduced to the planar coil. Measurements show that the magnetic core configuration improves the sensitivity of the assembly by a factor of 1.6. Depending upon theconditions, such as frequency and current bias, unamplified sensitivities from 8.6 to 10 muV mA-1 were observed.