Analysis of the measurement sensitivity of multidimensional vibrating microprobes

A comparison is made between tactile and vibrating microprobes regarding the measurement of typical high aspect ratio microfeatures. It is found that vibrating probes enable the use of styli with higher aspect ratios than tactile probes and are still capable of measuring with high sensitivity. In addition to the one dimensional sensitivity, the directional measurement sensitivity of a vibrating probe is investigated. A vibrating microprobe can perform measurements with high sensitivity in a space spanned by its mode shapes. If the natural frequencies that correspond to these mode shapes are different, the probe shows anisotropic and sub-optimal measurement sensitivity. It is shown that the closer the natural frequencies of the probe are, the better its performance is when regarding optimal and isotropic measurement sensitivity. A novel proof-of-principle setup of a vibrating probe with two nearly equal natural frequencies is realized. This system is able to perform measurements with high and isotropic sensitivity.