Fabrication and characterization of stacked ZnO and ZnOGa2O3 layers for the realization of bulk acoustic wave resonated membranes

ZnOGa2O3 alloys have been deposited by electron beam co-evaporation technique below the piezoelectric radio frequency magnetron sputtered ZnO films, with the aim of reducing the compressive stress due to the piezoelectric zinc oxide elaborated by radio frequency magnetron technique. The structural characterizations of the Ga2O3 thin films show an amorphous structure. Co-evaporating gallium oxide with zinc oxide has improved the optical and structural qualities of the e-beam zinc oxide films. Thus, deposing compressive rf magnetron sputtered piezoelectric ZnO on tensile thin layers of ZnOGa2O3, has reduced the stress and improved the structural quality of the realized bulk acoustic wave resonators. The fabrication of less stressed ZnO resonators has permitted to liberate partially our membranes by attacking the silicon substrate on which the resonator is realized. Finally, hyper frequency characterizations have been done by a network analyzer to study the influence of the silicon substrate thickness on the piezoelectric activity.