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 /spl mu/m 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 /spl mu/m and the length is 1000 /spl mu/m. 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 /spl mu/m. 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.