Fabrication of SAW Device By Using Zno Thin Film as a Sensing Area S.L.Lai, M.R. Zakaria School of Microelectronic Engineering Universiti Malaysia Perlis (UniMAP), Arau, Perlis, Malaysia leng_lai90@gmail.com, rosydizakaria@yahoo.com U. Hashim, K.L Foo, R. Haarindra Prasad Institute of Nano Electronic Engineering Universiti Malaysia Perlis (UniMAP), Kangar, Perlis Malaysia uda@unimap.edu.my Abstract— The limitation of human five main senses to detect the Nano-scale organism has introduced the idea for researcher in development several kinds of devices or sensors. The Surface Acoustic Wave (SAW) devices which wisely use in telecommunication field at the early time had been integrated into biosensor which able to detect the microorganism in aqueous state. Typically, a SAW sensor will have three elements which are transducers, sensing area and electronic signal processor. Zinc Oxide (ZnO) thin film use as piezoelectric substrate while metallic material as Inter Digital Transduces (IDTs). The new device structure which replaces the sensing area by using ZnO metal oxide layer is conducted in this study. Hence, the purpose is to investigate the behavior of various sizes of ZnO metal oxide layer as sensing area for the SAW device. Conventional lithography and Therefore, ZnO thin film layer by Sol-gel method is applicable use as SAW device. ZnO Sol-gel coating method were used to fabricate the SAW device. The SAW device with ZnO metal oxide layer shows the attractive result. The electrical characteristic and frequency response were used to assess the behaviour of the SAW device. X-ray Diffraction (XRD) and Atomic Force Microscope (AFM) was used to evaluate the ZnO structures. Keywords— ZnO Sol-gel ZnO thin film , SAW Biosensor device I. INTRODUCTION Since the end of the 18th century, ZnO material has become attracted within the research community [1]. The large band gap of 3.30 eV allows ZnO material endorses some specific behavior in term of their physical and chemical properties[3]. The outstanding properties of the ZnO lead to the development for several applications such as piezoelectric devices, SAW devices, chemical sensor as well as biosensor [2,3]. ZnO used as sensing material on the sensor which can achieve excellent sensitivity, even though there is a small sample for detection [3,4]. SAW-base biosensors have higher mass sensitivities and allow a higher frequency range from several 100MHz to a few GHz [5]. SAW device is sensitive to small change of mass loading. The change of mass loading effect the surface conductivity of SAW device thus it modified the waveform and result as output. A typical SAW sensor consists of a pair of IDTs and a sensing area between the IDTs. An IDT use to generate surface acoustic wave as the input another IDT use to transduce the mechanical wave into electric signals. The wave travels along the sensing area which initially coated with some material for selective detection. Any reaction takes place at the sensing area will result the modification of the traveling wave due to the change of propagation velocity[6]. There are several types of method to deposit ZnO thin films on the SAW device as piezoelectric substrate likes sputtering, Chemical Vapor Deposition (CVD) and Metal Organic Chemical Vapor Deposition (MOCVD), laser ablation, Molecular Beam Epitaxy (MBE), Sol-gel and Filtered Cathodic Vacuum Arc (FCVA) [7]. Recently, deposition by ZnO powder has been studied through ultrasonic spray pyrolysis [8], microwave-assisted synthesis[9] and sol-gel direct precipitation [10]. Among the deposition methods, sol-gel method is commonly used in the study purpose due to its relative low cost as compared to other methods [4]. The aim of this research is to fabricate a ZnO based SAW sensor with ZnO thin film as sensing area. The surface morphology of ZnO film was detected by using AFM while XRD was used to determine the crystalline structure orientation of ZnO thin film. II. EXPERIMENTAL PROCEDURE A. Mask Preparation For mask design, AutoCAD software was used to design the mask for the conventional fabrication process. Two masks design is needed in order to fabrication difference material layer on the substrate. The first mask is for IDT mainly to deposit the aluminum IDT electrodes and the second mask is for sensing area development which uses to allocate the ZnO thin film on the sensor. The IDT parameters are shown in Table 1. The mask design is illustrated in Fig. 1. TABLE I. MASK DESIGN PARAMETERS Criteria Parameters Finger width (um) 300 Finger length (um) 4500 Number of IDT finger 10 Aperture (um) 4200 Size of bond pad (um) 2000 x 2000 Size of sensing area (um) 4800 x 3000 IEEE-ICSE2014 Proc. 2014, Kuala Lumpur, Malaysia 380 978-1-4799-5760-6/14/$31.00 ©2014 IEEE