Surface acoustic wave filters in ZnO-SiO2-Si layered structures

The monolithic integration of SAW (surface acoustic wave) devices in a ZnO-SiO₂-Si layered structure with high-frequency electronic circuitry has been demonstrated. The high-resolution technology for the fabrication of the aluminum interdigital pattern-electron beam lithography, bilayer masking, and dry etching-is explained and illustrated with SEM (scanning electron microscope) photographs. Experimental results on a SAW delay line, a SAW transversal filter, and a SAW resonator filter show the feasibility of obtaining on-chip selectivity with SAW filters. A passivation of the sputtered, piezoelectric ZnO layer has been realized with a thin silicon nitride layer, resulting in an increased stability of the frequency response of the SAW device. A single-chip FM upconversion radio receiver with an on-chip SAW filter is discussed