Piezoresistive CMOS sensors for out-of-plane shear stress

This paper reports the development and characterization of a novel piezoresistive CMOS stress sensor enabling the measurement of the out-of-plane shear stress components ¿
_xz
and ¿
_yz
by exploiting the shear piezoresistive effect, i.e. the pseudo-Hall effect. The sensing structures are fabricated using a commercial CMOS process. They include a vertical current channel and two pseudo-Hall sensing contacts. In order to characterize the sensor elements, a setup comprising a silicon bridge with SU-8 posts was developed to induce well defined and homogeneous vertical shear stress in the chip surface. This vertical shear stress setup is analyzed using finite-element (FE) simulations. Measurements demonstrating the sensor concept show a linear sensor response with a sensitivity of 0.092 V/(A MPa).