Piezoresistive CMOS-compatible sensor for out-of-plane shear stress

A piezoresistive CMOS-compatible sensor for measuring the temperature-compensated out-of-plane shear stress components σxz and σyz is analyzed, implemented, and applied. The device exploits the shear piezoresistive effect due to vertical (out-of-plane) shear stress components. Possible sensor geometries are discussed and sensitivity considerations based on an affine transformation are presented. A bi-directional, 53 μm × 53 μm-large sensor design measuring two output voltages linearly proportional to the vertical shear stress components σxz and σyz is introduced. The experimental characterization of 17 such structures revealed an offset of the measurement voltage of −1.3 ± 0.6 mV and a linear sensitivity of −320 ± 85 μV/MPa. A variation of the supply voltage from 0 V to 5 V modulates the sensor resistance and voltage-related sensitivity by +6% and −12%, respectively. The geometry dependence of the sensitivity is evaluated using a finite element analysis. Design guidelines are extracted from these simulations. A demonstration of the sensor performance in an application concludes this paper.

► We present a piezoresistive sensor for measuring the shear stresses σxz and σyz.
► A bi-directional, 53 μm × 53 μm-large sensor is introduced.
► The sensing principle is explained by an affine mapping.
► Experiments using 17 sensors revealed a linear sensitivity of −320 μV/MPa.
► Design guidelines are extracted from FEM simulations.