Dimensional measurement of microholes with silicon-based micro twin probes

A new measurement method to characterize inside profiles of microholes regardless of materials is described in this paper. In order to apply this method, the fabrication technique of a silicon-based micro twin-probe was developed, and the fabrication process is presented. A microhole with a diameter of around 125 μm was actually measured using this method with micro twin-probe. Moreover, we succeeded in the fabrication of advanced long micro twin-probes with considering distribution of the residual stress, and investigated the mechanical characteristics of the probes. The thickness of the probes is 20 μm and the length is 1000 μm. To improve the measurement precision, we designed a new holder of a micro twin-probe and we evaluated the measurement reliability using the silicon-based long micro twin-probe. The estimated precision of measurement on this setup is smaller than 0.5 μm. The probes are designed so as to realize a higher resonant frequency than the driving frequency in measurement. The actual resonant frequency was measured by the laser Doppler instrument. A predicted resonant frequency is in good agreement with the experimental value. These results demonstrate that the micro twin-probe is evidently suitable for the measurement of inner surfaces of microholes