Effect of p-type and n-type piezoresistors on characteristics of high sensitive silicon piezoresistive microcantilever designs

This study presents four new silicon piezoresistive microcantilevers designs for biosensor application and compares their surface stress sensitivities for p-type and n-type piezoresistors. One basic and three variant designs with the piezoresistor inscribing the rectangular holes are proposed. The piezoresistors are placed in the high stress concentration regions near the cantilever base for achieving maximum sensitivity. Mathematical models for cantilever deflection and piezoresistor stress are derived and verified using finite element software. The designs are studied for operating conditions involving surface stress, ambient temperature and operating voltages. Results show that the average longitudinal stress in the piezoresistor of variant models is more than three times the average transverse ones, and that p-type cantilevers are better than n-type in piezoresistive microcantilever biosensor application.