Design consideration and finite element modeling of MEMS cantilever for nano-biosensor applications

This work has focused on the design and finite element modeling of a MEMS cantilever beam for biosensor applications. The stress induced on gold surface with polysilicon piezoresistive sensing is demonstrated. In principle, adsorption of biochemical species on a functionalized surface of the microfabricated cantilever will cause a surface stress and consequently the cantilever bending. The sensing mechanism relies on the piezoresistive properties of the polysilicon wire encapsulated in the beam. The beam is constructed and bending analysis is performed so that, the beam tip deflection could be predicted. The twelve independent beams were combined onto a single chip. The piezoresistor designs on the beams were varied, within certain constraints, so that the sensitivity of the sensing technique could be studied. The chip was laid out using Tanner L-edit and the design rules of the MUMPs process were followed. The device model was simulated using CoventorWareIM, a commercial finite element analysis (FEA) tool designed specifically for MEMS applications. Finally, the MEMS cantilever beam was operated and caused increment in tip deflection due to biochemical adsorption on the gold surface.