Effect of holes and edges on the squeeze film damping of perforated micromechanical structures

This paper investigates the squeeze film damping of a perforated planar micromechanical structure that oscillates in the normal direction to the substrate. Special focus has been placed on the size and number of perforations influencing the squeeze film damping. Theoretical models and test structures of the squeeze film damping have been developed for the transversely oscillating perforated plates. A set of nine different test structures, having three different sizes with three different numbers of perforations, has been fabricated and tested. The experimental Q-factors, measured from the fabricated test structures, are compared with the theoretical values, estimated from finite element analysis. It is found that the finite element analysis overestimates the Q-factors up to 150% of the experimental values. Major discrepancy comes from the inaccuracy of the zero pressure condition, placed by the finite element analysis along the perforated edges.