Piezoresistive response of five-contact vertical Hall devices

This paper reports on the piezoresistive effect and resulting offset behavior of CMOS-based five-contact vertical Hall sensors (VHS) under mechanical stress. Single sensor elements and coupled sensor systems comprising four individual VHS were exposed to normal in-plane stress σ_xx along the sensor axis using a four-point bending bridge setup. The resulting stress sensitivity of the offset signal at a bias voltage of V_bias = 3 V was below 2 μV/MPa. In addition, an inhomogeneous stress distribution was generated applying vertical forces close to a four-sensor system using a polymer cylinder. A resulting maximum offset increase by 20 μV/N at V_bias = 3 V was achieved. In conclusion, the influence of mechanical stress on the offset behavior of VHS is small compared to other offset sources such as the junction field effect and variations in sensor geometry.