Cantilever sensor with stress-concentrating piezoresistor design

A novel approach for enhancing the sensitivity of piezoresistive cantilever sensors is presented. Thin piezoresistive clamped-clamped silicon beams are released on the surface of the cantilever by a micromachining process sequence combining deep-reactive ion etching and anisotropic wet etching of silicon. A deflection of the cantilever sensor yields a stress concentration in these micromachined piezoresistive structures. Finite element simulations indicate an increase in both force and displacement sensitivity compared to a conventional cantilever beam with the same thickness. Devices have been fabricated and initial characterization has been performed. Under constant tip deflection of the cantilever, the new piezoresistor design shows an increase in the relative resistance change by a factor of 5.2 compared to a cantilever with the same thickness and conventional piezoresistor design