Fabrication of a CMOS-compatible surface acoustic wave device for application in pathogen sensing

Surface acoustic waves (SAW) devices have been initially developed and used for the high-volume low-cost TV component. Due to the ultra-sensitivity to the surface perturbation, SAW based devices have been modified to be sensors. Initially, SAW based sensors were developed for gas detection and recently they have been moving towards biological detection. Shear horizontal surface acoustic wave (SHSAW), one of the SAW based type is most suitable for the application in liquid based condition. Ultra sensitive pathogen sensors are needed to improve the food security and quality of life as well. Hence, the ultra-high sensitive biosensor has been designed in this research towards the low concentration pathogen detection. One of the main SHSAW components is the interdigital transducer (IDT). Currently, there are variety of techniques to fabricate the accurate size electrodes, Electron beam lithography and X-ray lithography. However, these methods are very costly. Therefore, this paper is presenting the more economical fabrication process which is using complementary metal-oxide-semiconductor method to fabricate inter-digital transducers on 64⁰ YX LiNbO₃ piezoelectric substrate. Comparisons were made for the theoretical calculation and fabricated measurement resonant frequency of the 3μm, 8 μm, 12 μm, 25 μm and 20μm width IDTs and the differences obtained are less than 5%.