Measuring the deflection of a micromachined cantilever-in-cantilever device using a piezoresistive sensor

We have designed and tested a piezoresistor for detecting deflection of micromachined Cantilever-in-Cantilever devices making use of the polycrystalline silicon film of the Mitel 1.5 /spl mu/m CMOS IC fabrication process. Both static deflection and resonance measurements have been investigated. The change of piezoresistance is about 0.06% under static deflection, which agrees with the ANSYS simulation results. Under dynamic excitation, the piezoresistance AC signal varies linearly with angular deflection of the cantilever, although the variation depends on the resonance mode. The resonant frequencies of the modes can readily be determined using the piezoresistor.