Simulations of piezoresistive microcantilever sensors for surface stress measurements

A finite element model was used to optimize the parameters for a surface-stress sensitive piezoresistive microcantilever sensor.The piezoresistive microcantilever sensors were optimized for various doping types by combining simulation and piezoresistive theory.A two-layer silicon cantilever was modeled with initial stresses applied to the top layer to simulate the surface stress.The stresses predicted by the simulations and the piezoresistive coefficients were used to analyze the dependence of the microcantilever sensitivity on the doping types and the length,width,and position of the silicon piezoresistor.The results show that n-type silicon piezoresistors should be long while p-type silicon piezoresistors should be short and placed in the root of the microcantilever to obtain higher sensitivities.Design guidelines are given for piezoresistive microcantilever sensor for surface stress biosensor measurements.