Fabrication and characterization of zinc oxide based surface acoustic wave devices

Abstract

Surface acoustic wave (SAW) devices, as applied to today’s technology, were first described in 1965. Since then, these devices were applied to a wide variety of fields. Bandpass filter is their most common application, which is an important component in consumer products such as televisions and mobile phones. SAW devices can also be utilized as chemical and biological sensors. Driving force behind the development of SAW sensors is their small size, high sensitivity, reliability, and durability. This thesis presents the development and characterization of ZnO/Si based SAW devices. ZnO thin films with c-axis orientation were deposited using rfmagnetron sputtering. Effect of post deposition annealing on the structure of ZnO and on the SAW device performance was studied. It was found that annealing ZnO above 600o C is detrimental for SAW device performance. Surface roughness of ZnO increases as the annealing temperature increases. In literature, roughness increase is presented as one of the reasons behind device breakdown. This work shows that roughness is not the primary cause for the breakdown. In addition, effect of SiO2 interlayer insertion between ZnO/Si structure on the device performance was examined together with the effect of ZnO thickness.