Size effect on the microbridges quality factor tested in free air space

The influence of geometrical dimensions on the dynamical response of polysilicon microbridges is experimentally investigated and presented in this paper. The main goal is to determine the quality factor variation of microbridges if the samples length is modified. The quality factor is an important qualifier of mechanical micro-oscillators and provides information about the loss of energy during oscillations. The loss of energy in an oscillator structure depends on the sample geometry, the material properties and also is influenced by environmental conditions. In this paper the dynamic response of electrostatically actuated polysilicon microbridges fabricated in different geometrical dimensions is investigated. The geometrical dimensions have a significant influence on the frequency response of microbridges. Indeed, the oscillator stiffness, velocity and amplitude of oscillations, quality factor and the loss of energy coefficient are changed as a function of the samples dimensions. A high value of the quality factor and a low loss of energy coefficient are determined for microbridges with small length fabricated in the same width and the same thickness.