Film Bulk Acoustic Resonator Based on Zinc Oxide Thin Film

A piezoelectric thin film sandwiched between two metal electrodes is basic structure for high frequency bulk acoustic wave devices. For that propose, the RF magnetron sputtering deposition for piezoelectric ZnO film formation and its such application for film bulk acoustic resonator (FBAR) devices are presented. Several critical parameters of the RF magnetron sputtering process deposition pressure, RF power, substrate temperature, O2 concentration and the target to substrate distance were determined to clarify their effects on the material characteristics of the ZnO. Highly c-axis oriented thin films as thick as 5.7 mm were grown and analyzed. Compressive stresses were observed. The FBAR devices with the ZnO films exhibited a pronounced resonance peak centred at 537 MHz with a k2 coupling coefficient of 7 %. It found therefore that the impedance matching of the FBAR could be easily achieved simply by controlling the resonance the resonator. Keywords: ZnO; FBAR; R.F sputtering magnetron; resonator

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

International audienceZnOGa"2O"3 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 Ga"2O"3 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 ZnOGa"2O"3, 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