Mechanical Behavior of a Mems Acoustic Emission Sensor

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Abstract
The elastic modulus and hardness of materials used in a MEMS acoustic emission sensor were determined using nanoindentation techniques. In addition to testing each individual material, the behavior of four candidate bottom electrode structures, two based on nitride layers and two based on oxide layers, have been evaluated. The multilayer nitride bottom electrode is relatively unaffected by a 950 °C annealing step; however, some evidence of second phase formation in the polycrystalline silicon layer has been observed. Increasing the thickness of the thermally grown silicon dioxide in the oxide based electrodes lowers the measured hardness of the top layer of platinum while increasing the measured modulus of the entire electrode at depths corresponding to the oxide film. Errors of up to 25% in the calculated area of indentation based on the indenter shape function occur for indentations which penetrate both the platinum and oxide films.