Characteristics of Zinc Oxide Films on Glass Substrates Deposited by RF-Mode Electron Cyclotron Resonance Sputtering System

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Abstract
There are two types of electron cyclotron resonance (ECR) sputtering systems, DC-mode and RF-mode. In this paper, the properties of zinc oxide (ZnO) film deposited by an RF-mode ECR sputtering system capable of long-term stable deposition are investigated. It is confirmed for the first time that this system is capable of depositing a ZnO film having a sidewall structure without columnar or fibrous grains on an interdigital transducer (IDT)/glass substrate. The ZnO films so deposited were capable of driving the 1.1 GHz fundamental mode in a Rayleigh surface acoustic wave (SAW) without the large propagation loss at high frequencies of conventional ZnO films. Furthermore, ZnO films deposited by this system exhibited 1.7 dB lower insertion loss and a closer agreement between effective electromechanical coupling factors (k eff) and the corresponding values calculated with the finite element method (FEM) in comparison with the films deposited by the DC-mode ECR sputtering system.