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Journal of Nanomaterials
Volume 2014 (2014), Article ID 643672, 10 pages
http://dx.doi.org/10.1155/2014/643672
Research Article

Design and Fabrication of Nanoscale IDTs Using Electron Beam Technology for High-Frequency SAW Devices

1Department of Electrical Engineering, National Sun Yat-sen University, No. 70 Lienhai Road, Kaohsiung 80424, Taiwan
2Department of Electronic Engineering, De Lin Institute of Technology, Lane 380, No. 1 Qingyun Road, Tucheng District, New Taipei 23654, Taiwan
3Department of Computer and Communication, Shu-Te University, No. 59 Hengshan Road, Yanchao District, Kaohsiung 82445, Taiwan

Received 13 December 2013; Accepted 21 February 2014; Published 7 April 2014

Academic Editor: Liang-Wen Ji

Copyright © 2014 Wei-Che Shih et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

High-frequency Rayleigh-mode surface acoustic wave (SAW) devices were fabricated for 4G mobile telecommunications. The RF magnetron sputtering method was adopted to grow piezoelectric aluminum nitride (AlN) thin films on the Si3N4/Si substrates. The influence of sputtering parameters on the crystalline characteristics of AlN thin films was investigated. The interdigital transducer electrodes (IDTs) of aluminum (Al) were then fabricated onto the AlN surfaces by using the electron beam (e-beam) direct write lithography method to form the Al/AlN/Si3N4/Si structured SAW devices. The Al electrodes were adopted owing to its low resistivity, low cost, and low density of the material. For 4G applications in mobile telecommunications, the line widths of 937 nm, 750 nm, 562 nm, and 375 nm of IDTs were designed. Preferred orientation and crystalline properties of AlN thin films were determined by X-ray diffraction using a Siemens XRD-8 with CuK radiation. Additionally, the cross-sectional images of AlN thin films were obtained by scanning electron microscope. Finally, the frequency responses of high-frequency SAW devices were measured using the E5071C network analyzer. The center frequencies of the high-frequency Rayleigh-mode SAW devices of 1.36 GHz, 1.81 GHz, 2.37 GHz, and 3.74 GHz are obtained. This study demonstrates that the proposed processing method significantly contributes to high-frequency SAW devices for wireless communications.