Process-tolerant Surface Acoustic Wave delay lines

Abstract

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 LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> substrate. It is designed with specific IDT feature size to produce SAW at predetermined central frequency, f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> . 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 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , and hence a process-tolerant SAW delay lines.