Suspended submicron silicon-beam for high sensitivity piezoresistive force sensing cantilevers

This paper presents a submicron suspended piezoresistive silicon-beam structure as a basic sensing element to replace the conventional piezoresistors, so to improve detection sensitivity. The alternative element benefits from the increase in the stress, locally concentrated on the suspended submicron beam, induced by mechanical loads. This approach allows the enhancement of sensitivity without changing the parameters in the mechanical design. A modified deep reactive-ion etching process is developed to create both the suspended silicon-beam and the main mechanical structure in a single etching sequence. The suspended beam is integrated in a silicon force sensing cantilever. A force sensitivity up to 52.5 V/N is obtained, corresponding to a 120% improvement compared to an equivalent structure with conventional piezoresistors.