A piezoresistive microcantilever array for surface stress measurement: curvature model and fabrication

This paper presents a procedure for the fabrication of a piezoresistive microcantilever array for surface-stress-based chemical and biochemical sensing applications. All existing microcantilever surface stress sensors that are based on single-crystal silicon use p-doped piezoresistors. In this work, the advantages of using n-doped silicon piezoresistors for surface stress sensing have been demonstrated. Further, a new model for surface-stress-sensitive cantilevers, based on classical laminated plate theory, is presented. This model allows for the estimation of the deformation and piezoresistive response of a multilayered microcantilever to surface stresses during analyte measurement and residual stresses in the structural layers due to fabrication processes. Also, the model accounts for bending-stretching coupling in the microcantilever response to the stresses. The utility of the model as a design tool for control of cantilever curvature during the fabrication process has been demonstrated.