Abstract
An improved rf sputtering system for manufacturing ZnO thin-film devices is described. The system consists of a hemispherical electrode geometry with a ZnO center cathode and provides c axis highly oriented ZnO films onto 60 sheets of glass substrate wafers of 25 mm square in one sputtering run. The growth rate of ZnO films is 0.3–0.7 μm/h. The film thickness variations in these wafers are within ±1%. The electrical resistivity of the films ρ?106–107 Ω cm, dielectric constant ε*?8.5, the electromechanical coupling in a longitudinal mode kt?0.23–0.24, in a Rayleigh mode keff?0.07–0.085 for the ZnO film thickness of 3% of the wavelength. The present system enables the manufacture of the ZnO thin-film SAW filter with a frequency accuracy, better than ±0.1%, and a temperature stability, better than −10 ppm/°C.
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