Reducing the probe ball diameters of 3D silicon-based microprobes for dimensional metrology

Microprobing systems based on silicon force sensors allow accurate force and displacement measurements in the range of several μN or μm. Due to the high sensitive diffused piezoresistors and an appropriate electrical circuitry, these probing systems enable tactile measurement without leaving scratches on the probed surfaces. To probe microstructures on workpieces, probes with probe balls as small as possible are sought. Mostly, commercial microprobes have probe balls with diameters of 120 μm or larger. In this work, microprobes with probe ball diameters down to 50 μm are presented and characterized in detail. In order to verify the performance of these new microprobes, measurements have been carried out to characterize both their mechanical behavior and their sensitivity. These properties have been extensively analyzed for different sensor designs and probe ball diameters. For instance, microprobes with probe ball diameters of 50 μm have a stiffness of about 0.637 mN/μm in X-Y and about 20.023 mN/μm in Z directions of the probe. The sensitivity amounts to 1.174 mV/V/μm and 20.478 mV/V/μm in X-Y and Z directions, respectively. The results presented encourage a new generation of microprobes to be used in dimensional metrology.