Tactile probes for dimensional metrology with microcomponents at nanometre resolution

Abstract

Dimensional metrology with microcomponents using tactile probing is addressed. For this purpose, slender cantilever sensors have been developed which are specially designed for the characterization of geometrical features of a high-aspect ratio. The cantilever comprises a low-noise piezoresistive strain gauge avoiding the geometrical restrictions by the conventional optical read-out of atomic-force probing cantilevers. Prototype sensors of a length 1.5 to 5 mm, width 30 to 200 µm and height 25 to 50 µm with an integrated probing tip have been realized using silicon bulk micromachining. Calibration of the cantilevers revealed nanometre resolution within a vertical tip position range of a few hundred microns. The sensor performance was tested by profiling thickness, groove and roughness artefacts at several tens of µN probing force and mm s−1 scan velocity confirming ruggedness and exploiting low inertia of the novel cantilever sensors. Close agreement with the calibration sheet data was found as well as low wear of a few nanometres per metre scan length which was detected during scanning over a steel artefact confirming the potential of the sensor for high-throughput in-process metrology.