Determining the high-temperature properties of thin films using bilayered cantilevers

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Conference Proceeding

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Materials Research Society Symposium - Proceedings

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High-temperature applications of microelectromechanical systems (MEMS), especially in new temperature sensor designs, require an accurate knowledge of the temperature-dependent thermophysical properties of the materials. Although the measurement of the mechanical properties of materials at room temperature has been widely conducted, the same techniques often cannot be used for high-temperature property measurements. In this study, a new technique was developed to find the thermal expansion coefficient of thin films at high temperatures. Bilayered cantilever beams undergo thermally induced deflection at high temperatures, which can be measured and correlated to material properties. An imaging system was developed for the experimental measurement of the beam curvature for temperatures up to 1000 °C. To find the high-temperature property of thin films, a bilayered beam, consisting of polycrystalline silicon and silicon dioxide, was designed such that the change in the property of SiO2 had little effect on the curvature of the beam. Furthermore, numerical analysis showed that the Young's modulus of Si also had negligible effect on the curvature. Therefore, the analytical model for beam curvature was simplified to be only a function of the thermal expansion coefficient of Si layer. Using this model, the thermal expansion coefficient of polycrystalline Si film was determined for temperature range between room temperature and 1000 °C. The method can be easily modified to find the Young's modulus of Si, as well as properties of SiO2.



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