Meta-materials approach to sensitivity enhancement of MEMS BAW resonant sensors

This paper demonstrates for the first time the use of meta-materials (MTM) in bulk acoustic wave resonators (BARs) for sensing applications under atmospheric pressure conditions. Key is the observation that implementing square holes in the BARs modifies their specific surface area (area-to-volume ratio) and lowers their mass. We establish through simulations and measurements that increasing the perforation density and decreasing the perforation pitch both improve the sensitivity of BARs, in the limit becoming independent of the BAR thickness. The thickness can thus be increased without paying a penalty in lowering the motional impedance of the BARs, while easing the specifications for drive and readout circuitry. We finally report a measured improvement in DNA detection sensitivity by more than one order of magnitude enabled by introducing MTM in BARs implemented in the SiGe-MEMS process from IMEC.