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Mechanical characterization of microelectronic structures by optical vibrational measurements

The tools of the optical measurement of deformation are increasingly used to characterize the mechanical as well as thermal properties of MEMS or microcomponents. Both, the residual stress state and thermally induced deformation can be analyzed by applying of laser Doppler vibrometry or by several variants of laser based optical methods usually using photoelectric detection. In the paper the application of techniques for the dynamic movement and vibrations measurement of microelements and thin silicon membranes is reported. Using the laser Doppler vibrometry is discussed to evaluate the stress state of membrane-like microbridges, to obtain frequency characteristic and impact response of microcantilever and to measure the resonances of thin silicon membranes. Based on observation of time-averaged light intensity pattern at focal plane, newly developed method of autocollimation is demonstrated with the possibility to visualize the vibration mode shapes of membranes. Beside this, also the experience with laser deflection detecting by position sensitive detector technique is described.