| With the growth of micromachining process technologies for microelectromechanical systems (MEMS), the surface micromachining technique has been increasingly used in the fabrication of sensors and actuators. Control of material property (e.g. residual stress, Young's modulus) in a thin film becomes important in the processing of surface micromechanical structures. Therefore, it is getting more and more important to extract film material property by the in-situ method.An analytical expression of pull-in voltage for a doubly-clamped multi-layer beam with different widths under an electrostatic load is obtained by using the energy method, and is fitted by the numerical analysis. It is the first time to get the analytical expression with error less than 2.5%. Since the pull-in voltage is related to material properties and geometry of the beam, a novel extracting method for material properties of the multi-layer film based on designed beams with different widths is presented for the first time and related Matlab scripts have been programmed. Comparison of results from the analytical expression and those from Coventorware shows that they agree with each other great well. In order to confirm sufficient measuring precision, the suitable geometry of the beams and the form of anchors has been determined based on a specified process. Considering all of these, layout has been designed. This method requires only very readily available test equipment and occupies very small area of the chip, so it can be used in MEMS process and in-situ monitoring.
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