Metallizations for surface acoustic wave resonators. Film properties and device characteristics

All-quartz packaged surface acoustic wave (SAW) resonator devices with interdigital transducers fabricated using electron-beam evaporated aluminium or copper-doped aluminium films which incorporate small amounts of either silicon or titanium are evaluated. The electrical characteristics discussed include: sealing-induced frequency shifts and residual flicker noise, as well as random and systematic long-term frequency stabilities. The data obtained thus far indicate that doping the interdigital transducers with a combination of both copper and titanium can result in SAW resonator devices with both excellent residual flicker noise and long-term frequency stabilities, even when the devices operate under conditions resulting in extremely high acoustic stress levels. In contrast, resonator devices fabricated using aluminium films doped with only silicon or titanium display both poor flicker noise and long-term frequency stabilities, even when operated at relatively modest stress levels