Fig. 4: Schematic fabrication process of the resonator chip.

a Thermal oxidization. b Mo film deposition. c AlN film deposition. d Metal layer sputtering. e LPCVD SiO2 layer deposition. f Bonding pad exposure. g Bottom electrode exposure. h Bonding pad formation of the bottom electrode. i Microcantilever-based resonator release. j Fabricated piezoelectric resonator chip, including SEM image and detailed LSCM image. k Experimental platform of the resonator chip for liquid sensing