Logo of the Physikalisch-Technische Bundesanstalt
symbolic picture: "magazines"

Probing of complex micro- and nanostructures

Novel micromechanical sensors have brought production control of complex  micro- and nanocomponents a decisive step forward. These sensors allow the   position, form, measure – and even the roughness – to be metrologically determined also on vertical walls of smallest structures. Core piece of the sensors – for which a patent has been applied for – are cantilevers as they are also known from scanning force microscopy.

While the microprobe measures the vertical flank of a microgear,
the movement of the probe is read out optically. The
figure shows the holding chip with the cantilever and the vertical
probe shaft.

Already for some years, measuring instruments and microscopes have been available which enable lateral structures – down to nanostructures – on plane surfaces to be made visible. However, on rough surfaces, on structures with high aspect ratio or even on vertical object surfaces, precise measurements have so far not been possible.

These measurements can now be performed with the newly developed sensors. As in a typical scanning force microscope, the sensor consists of a horizontal cantilever. What is new is that to this cantilever, a vertical probe shaft is attached, with the probe tip at its end. The movements of the cantilever which occur  hen the measurement object is touched, or (in dynamic operation) the changes in the probe oscillation are determined by the optical beam deflection  method with the aid of a quadrant photodiode.

Due to the very small radius of the probe tips of approx. 20 nm, the lateral resolution of the new sensors – which are referred to as “ACPs” (Assembled Cantilever Probes) – is very high. Moreover, small contact forces of < 0.01 μN prevent a scratching of delicate surfaces. Another advantage of these sensors  is that they are composed of commercially available mass-produced microcomponents and can be adapted to the respective measurement task. For  pplications to microgears and to line edges of printed circuit boards, standard deviations of approx. 1 nm have already been achieved.

It is envisaged to replace the simple probe tip used so far with a star-shaped probe which effects the three-dimensional measuring capability of the ACP  sensors. If these sensors are then used in 3D measuring systems (e.g. coordinate measuring machines), an effective solution for testing the quality of  complex micro- and nanoproducts can be expected for the near future.

Contact at PTB:

Phone: +49-531-592-0