A multi-material resonant thin film beam for a micromechanical sensor having azero temperature coefficient of frequency (TCF)which is the resonant frequency shift with temperature change. One of thematerials may be polysilicon and the other material may besilicon nitride or silicon oxide. Each material has a different thermalcoefficient of expansion. The proportion of the various materials isadjusted and the specific geometries are determined so that the TCF is zero.One embodiment is a microbeam composed of two polysiliconthin films with a silicon nitride thin film inserted between the polysiliconfilms. The thickness of the silicon nitride film may be adjustedto trim the TCF to zero. The film of nitride instead may be placed on one sideof a polysilicon film to form a beam. Dual or multiplebeam resonators likewise may be made with several materials. The nitride maybe placed in the shank areas which join and secure the endsof the beams. Such zero TCF beams may be incorporated in microsensorstructures for measuring pressure, temperature, strain and otherparameters.
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