Sensitivity in nanomechanical pedestal MEMS cantilever

Abstract

Nanomechanical resonator-based sensing devices are used in medical diagnostics based on their high-frequency dynamic behavior. Cantilevers fall into the category of Nanomechanical resonators. It also resembles a resonator whose shape is like that of a nanowire clamped at one end. As the surface-to-volume ratio of a nanowire resonator increases due to scaling down, surface stress plays a crucial role in the mechanical behavior of a resonator. Piezoresistive MEMS cantilevers are used for vapor phase analysis of volatile compounds and gas. Studies were done to address the mass sensitivity issues and fractures associated with bioceramic and nanocomposite coatings-based cantilever resonators. The studies show how the sensing performance can be determined or tuned. Finite Element modelling of a pedestal cantilever resonator was done which takes into consideration the mass sensitivity issues associated with linear cantilevers. MEMS cantilever structures were fabricated using lithographic techniques. SiCN, a suitable material for MEMS in harsh operating conditions were deposited on Silicon substrates showing high hardness (20 GPa) and modulus (220 GPa). The electrical conduction taking place between the nanoindentation tip and sample was explored. The surface stress of 711 MPa was determined based on pedestal cantilever deflections, Fracture taking place on the sample surface was found to affect the conduction and tip displacements in AFM nanoindentations. The sharpness of the tip was found to have an influence on the tip-sample conduction mechanism useful for MEMS applications. The sensitivity associated with cell mass detection was reported to get affected by film deposition stress and formation of surface cracks and puts a challenge for doing future work.