Towards bendable CMOS magnetic sensors

Abstract

This paper analyses the bending-induced stress effects on ultra-thin cross-shaped magnetic sensors operating in voltage- or current-modes. Both the magnetic sensor's sensitivity and the offset drift have been analysed. The optimum geometry and thickness of the Hall sensor are the important parameters to be analysed to compensate any mechanical stress related effect on the performance of sensors. Numerical simulations are carried out using the finite element method (FEM) with COMSOL Multiphysicsr software. A compact model is implemented in Verilog-A and used for the simulations in Cadence® Spectre, considering a 350 nm CMOS process. The simulation results focus on magnetic sensor's sensitivity variation and offset drift induced by bending of the substrate. The simulation results show a sensitivity of 71 V/AT at 100 mT. Interestingly, the sensitivity variation induced by 250 MPa applied uniaxial stress is less than 0.02 %.