Development of Surface Acoustic Wave Device Sensor Using Optical Lithography

This work is aimed at developing Surface Acoustic Wave (SAW)-based wireless passive sensors for sensing volatiles, humidity, temperature and pressure. The development of this inexpensive passive SAW sensor would create a wide range of gas sensing applications. The SAW devices consist of a piezoelectric substrate such as quartz and interdigitated (IDT) transducers formed by optical lithographic patterning of a thin metal layer. The optical lithography employs 365 nm UV light source, exposing the geometric pattern mask onto a 2 μm layer thickness of AZ5214E positive photoresist, a new epoxy product from Microchemicals. The lithographic processes were optimised to achieve IDT feature size of 39 μm for 20.2 MHz RF signal transmission.