| Summary: | 碩士 === 國立交通大學 === 機械工程學系 === 100 === Residual stress due to the fabrication process might cause the deformation of MEMS devices. Using pull-in voltage to determine residual stress is possible to directly detect residual stress on MEMS fabrication process. In previous studies using pull-in voltage to detect residual stress, the tilting effect of cantilever beam was not been taken into consideration. This study proposed a modified deformation function, which considered both curl and tilt deformation caused by gradient stress and mean stress. And this proposed deformation function was used to evaluate the pull-in voltage of the cantilever beam.
In test experiment, the cantilever is made of poly-silicon, with three different lengths, 256um, 300um and 330um. The tilt angle and radius of curvature can be determined by white light interferometer (WLI). By comparing the analytical result with measurement results on pull-in voltages, it is found that without considering tilting effect, the average mismatch between analytical solutions and experimental results on pull-in voltage is in a range of 6.02% to 15.20%. On the other hand, when tilting effect is considered, this mismatch is reduced to a range of -4.44% to 5.26% which verifies the improvement of the proposed analytical solution.
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