Experimental demonstration of microfabricated phononic crystal resonators based on two-dimensional silicon plate

This paper shows the design, fabrication and characterization of a novel design micromechanical resonators with Bloch-mode resonance by creating defects on a two-dimensional (2-D) silicon phononic crystal (PnC) slab made by etching a square array of cylindrical air holes in a 10m thick free-standing silicon plate. Piezoelectric aluminum nitride (AlN) film is deployed as the inter-digital transducers (IDT) to transmit and detect acoustic waves, thus making the whole microfabrication process CMOS-compatible. We also fabricate a PnC structure which has a stopband of 140MHz < f <195MHz which agrees quite well with the simulation results. The characterized resonant frequency of microfabricated PnC resonators increases with central-hole radius (r') and reaches its maximum value (163.54MHz) at r'=8μm, while Q factor reaches maximum (954) at r'=6μm. The Bloch-mode PnC resonators based on square lattice PnC structure show promising acoustic resonance characteristics with relative smaller PnC active area than other reported designs. Such performance is very promising for sensing applications.