Authors: ReChing Lin YingChung Chen KuoSheng Kao
Publish Date: 2007/06/29
Volume: 89, Issue: 2, Pages: 475-479
Abstract
This study investigates highperformance ZnO piezoelectric films used for thin film bulk acoustic resonators TFBAR The ZnO piezoelectric film was deposited on a Pt/Ti electrode using an RF magnetron sputter by a twostep method at room temperature The Pt/Ti electrode was deposited by a DC sputtering system on which ZnO piezoelectric films were deposited in one step and in two steps to minimize roughness in the first step and produce the preferred orientation in the second Both fieldemission scanning electron microscopy FESEM and atom force microscopy AFM revealed that ZnO piezoelectric film deposited by twostep sputtering exhibited favorable characteristics such as a rigidly precise surface structure with surface roughness of 737 nm even better than in onestep sputtering Examining the ZnO thin film by Xray diffraction XRD showed a much higher caxispreferring orientation than in onestep sputtering The reflection coefficient of the resonator device was measured using an HP8720 network analyzer The frequency response of the FBAR device exhibited a return loss of 25 dB at a resonant frequency of 2212 MHz with a high coupling coefficient of 67
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