Experimental study of the effects of size variations on piezoelectrically transduced MEMS resonators

We report results of a parametric study on a set of single-crystal-silicon plate resonators, whose lateral dimensions are varied so that the main resonance mode occurs at a range of f = 13...30 MHz. The resonator transduction is based on a piezoelectric AlN thin film. Measurements spanning >1000 devices and two wafers indicate that with certain device dimensions the square extensional resonance mode and a higher-order extensional mode are excited with a relatively low frequency scatter of Δf ~ 2 000 ppm (full range). Other resonance modes typically have a frequency scatter larger than 15 000 ppm, which we interpret to be an indication of their flexural character. Additionally, we observe a splitting of the main resonance mode branch at intermediate device dimensions.