Experimental and computational investigation of zinc oxide based surface acoustic wave devices

Abstract

Piezoelectric materials are used in different types of transducers such as microphones, accelerometers, speakers, hydrophones, pressure sensors etc. Compared to traditional bulk piezoelectric crystals, thin film piezoelectric materials are promising to realize integrated devices with CMOS technology. Among thin film materials, zinc oxide (ZnO) is attractive due to the giant piezoelectric effect when doped with vanadium. In this study, we investigate the deposition of thin film ZnO and V-doped ZnO films. Materials characterization of ZnO thin films is performed. We also investigate surface acoustic wave (SAW) devices based on ZnO thin films. SAW devices are formed by a pair of interdigitated transducers (IDTs), input and output IDTs. IDTs are fabricated onto the piezoelectric thin film. Applied oscillating electric field from input IDT creates surface acoustic waves in the piezoelectric thin film and these acoustic waves are converted back into an electrical signal at the output IDT. SAW devices based on ZnO and V-doped ZnO films were designed and fabricated. Frequency response of SAW devices is measured. In addition, finite element simulations of SAW devices are shown to be in agreement with measurement results. We discuss resonance frequency and insertion loss of SAW devices.