Design, fabrication and test of cantilever-type sensors for active micro force calibration are described. The cantilever comprises a probing tip at its free end where a force can be applied which is measured using a piezoresistive strain gauge at the cantilever suspension. The stiffness of the cantilever is approximately given by the spring constant of a beam with a rectangular cross section as confirmed by finite element modelling. Prototypes with a stiffness of 0.66 N m−1 and 7.7 N m−1 are realized using standard silicon bulk micromachining technology. Testing is performed using a high-resolution micro force measuring set-up. In either case a highly linear relationship between the gauge output voltage and the probing force is revealed in the µN range. Low scatter and drift corresponding to a standard deviation of ±0.22% was found for the resulting force sensitivity.

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We demonstrate the non-destructive measurement of the stiffness of single-beam, monocrystalline silicon cantilevers with a trapezoidal cross-section and tips as used for atomic force microscopy from the knowledge of cantilever dimensions, eigenfrequencies and material parameters. This yields stiffness values with an uncertainty of ±25% as the result critically depends on the thickness of the cantilever that is experimentally difficult to determine. The uncertainty is reduced to ±7% when the measured fundamental eigenfrequency is included in the calculation and a tip mass correction is applied. The tip mass correction can be determined from the eigenfrequencies of the fundamental and first harmonic modes. Results are verified by tip destructive measurements of the stiffness with a precision instrument recording a force-bending curve yielding an uncertainty better than ±5%.

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Sputter-deposited amorphous diamond-like carbon (DLC, a-C) on silicon has been investigated with respect to micro electro mechanical systems (MEMS) applications. Sputtered a-C with a content of diamond-like sp3 bonded carbon of around 25% showed a high hardness of up to 30 GPa. Self-supporting cantilevers of 0.5 µm in thickness, several hundreds of µm in length and some tens of µm in width have been successfully realized using lift-off patterning of DLC and anisotropic silicon etching. The mechanical properties of DLC (Young's modulus, stress, stress gradient fracture strength) were characterized by cantilever deflection analyses. DLC strain gauge resistors integrated on micromachined silicon boss membranes were investigated under tensile and compressive loading. Piezoresistive gauge factors in the range of 20–30 were observed at temperatures between room temperature and 50 °C.