ZERO TCF THIN FILM RESONATOR

摘要

A multi-material resonant thin film beam for a micromechanical sensor having a zero temperature coefficient of frequency (TCF) which is the resonant frequency shift with temperature change. One of the materials may be polysilicon and the other material may be silicon nitride or silicon oxide. Each material has a different thermal coefficient of expansion. The proportion of the various materials is adjusted and the specific geometries are determined so that the TCF is zero. One embodiment is a microbeam composed of two polysilicon thin films with a silicon nitride thin film inserted between the polysilicon films. The thickness of the silicon nitride film may be adjusted to trim the TCF to zero. The film of nitride instead may be placed on one side of a polysilicon film to form a beam. Dual or multiple beam resonators likewise may be made with several materials. The nitride may be placed in the shank areas which join and secure the ends of the beams. Such zero TCF beams may be incorporated in microsensor structures for measuring pressure, temperature, strain and other parameters.