Process-tolerant Surface Acoustic Wave delay lines

Surface Acoustic Wave (SAW) delay lines microfabrication is outlined and its characteristics due to wet chemical etching process variation are investigated. The SAW delay lines consist of Al inter-digital transducers (IDT) on LiNbO₃ substrate. It is designed with specific IDT feature size to produce SAW at predetermined central frequency, f₀. The effect of the etching process onto the IDT, in particular the feature size, is investigated using field emission secondary electron microscope (FESEM). The effect is then translated into transfer characteristics of the SAW delay lines by measuring its transmission and reflection coefficient using network analyzer. It is found that even with a ~5 μm IDT feature size variation due to the wet chemical etching process, the fabricated delay lines can still produce SAW at the designed f₀, and hence a process-tolerant SAW delay lines.