Precise dimensional measurements on microstructures require not only very precise measuring machines but also efficient microprobing systems. Each microprobing system must be metrologically checked and precisely calibrated before it can be incorporated into a micro-coordinate measuring system. The investigations serve to exactly determine systematic deviations to subsequently correct them.
The calibration device consists of commercially available components. In addition to the investigation of the static properties of microprobing systems, the work is mainly aimed at characterizing microprobing systems in dynamic terms in view of their potential use in so-called scanning measuring operations. In contrast to single-point probing, scanning dimensional measuring techniques offer considerably shorter measuring times and thus manufacture-oriented applications.

The 3D calibration device is composed of two sub-assemblies and allows coarse positioning (25 mm x 25 mm x 12.5 mm) as well as precise fine-positioning by a capacitively controlled flexible hinge table with an operating range of 80 µm. The coarse positioning table is made of special steel to ensure optimal long-time stability, and provided with cross-roller guideways of hardened steel which offer high stiffness and thus allow precise positioning. The angular deviations on each axis are smaller than 100 mrad. The table is operated with a DC servomotor in a closed control loop. The precise fine-positioning table is moved with the aid of piezoelements.

Prinzipskizze: Aufbau der 3D-Kalibriereinrichtung für Mikrotastsysteme

Figure 1: Schematic diagram 3d-calibration device of micro systems

A metrology frame which is at present equipped with two laser interferometers, allows Abbe error-free 2D microstructure probing in the nanometer range. The positional information and the probe signals can be simultaneously measured with a probing frequency of 5 kHz.

Systematic investigations into the efficiency of the calibration device, which had first been realized with two-dimensional interferometric positional metrology, have been carried out. The positioning noise of the x- and y-axes amounts to 12 nmp-p in a detection bandwith of 5 kHz.
Special probing strategies for microprobing systems have been tested. In the case of one-dimensional probing of an aluminium plate, a standard deviation of 20 nm was determined for the points probed. This order of magnitude is sufficient for the investigation of the dynamic properties and the calibration of 3D microprobing systems.