Working Group 5.11

Nanoforce Metrology for Tactile Sensors

• 3d-micro-probe
• Si-Cantilever sensors
• 3d-calibration device for the dynamical calibration of micro systems

Si-Cantilever sensors

Commercially available cantilevers with piezoresistive deflection detection were tested for use as roughness sensor at vertical sidewalls of micro structures with high aspect ratio. These cantilevers are in principle suited for this task, but two main drawbacks are observed: the tips and the cantilevers are too short.

In cooperation with the institute for semiconductor techniques (IHT) of Braunschweig technical university the development of Si-cantilever sensors with the following properties started:

• cantilever length 5 mm
• monolithic manufacturing
• additional wiring (like wire bonding) is not necessary since the electrical contacts are also realized on the chip
• the probing tip is also monolithically manufactured, thus no further assembly steps are necessary

First prototypes of these new sensors with pyramidal tip have been successfully realized and investigated concerning bending stiffness and electrical sensitivity. A good linearity of the force and the output voltage in dependence of the cantilever deflection was measured. The deviation of the force-deflection curve from linearity was only +/- 1 µN (0.5 %) and the deviations of the output signal-force curve were +/- 1 mV (0.3 %) corresponding to +/- 72 nm. These values were measured for a total cantilever deflection of 24 µm, which corresponds to a force acting on the tip of 180 µN.

Besides the simple pyramidal probing element angled and capacitive probing elements are scheduled.