MEMS cantilever sensor for non-destructive metrology within high-aspect-ratio micro holes

Tactile metrology with high-aspect-ratio micro holes was addressed using extremely slender piezoresistive micro cantilever sensors operated under axial loading. Linear strain-displacement characteristics were observed at small axial displacements. From noise and non-linearity measurements the resolution and uncertainty of the cantilever sensors were determined to ap 1 nm and < 10 nm, respectively, within a displacement span of 1.4 mum. Buckling of the cantilevers was observed after exceeding the critical load of an Euler beam under the boundary conditions of a clamped-pinned beam. The cantilevers typically survived displacements well above the buckling limit, i.e. fracture of 3-mm-long cantilevers was only observed at displacements of more then 200 mum. The feasibility of the cantilever as an active 1D touch probe for high-aspect-ratio blind holes was demonstrated at a dry-etched silicon microstructure.