A CMOS-COMPATIBLE 2-D VERTICAL HALL MAGNETIC-FIELD SENSOR USING ACTIVE CARRIER CONFINEMENT AND POST-PROCESS MICROMACHINING

This work presents a CMOS-based magnetic-field sensor for the detectio n of magnetic-field vector components that occur parallel to the chip surface. The device employs two vertical Hall plate structures embedde d in the substrate orthogonal to each other. The sensor is fabricated using a standard 3 mu m CMOS process provided by a commercial integrat ed circuit (IC) manufacturer, and a maskless post-process bulk-microma chining step. The sensor makes use of standard p+ implants to bound th e plate region for the purposes of: (a) actively confining majority ca rriers to a narrow channel, thereby enhancing sensitivity; and (b) act ing as an etch-stop layer. The micromachined cavities act to reduce de trimental cross-sensitivity effects. Sensitivity is found to vary with negatively increasing p+ confinement voltage, but appears to saturate due to a pinch-off effect.