Studies on MgxZn1-xO Thin Film Resonator for Mass Sensor Application

Ying Chen, Gaurav Saraf, Richard H. Wittstruck, Nuri W. Emanetoglu, Yicheng Lu

Abstract:	Zinc oxide (ZnO) and its ternary alloy magnesium zinc oxide (MgxZn1-xO) are piezoelectric materials for high quality factor bulk acoustic wave (BAW) resonators operating at GHz frequencies. MgxZn1-xO thin film BAW devices built on Si substrates are particularly attractive for integrating piezoelectric MgxZn1-xO with the main stream semiconductor devices and circuits. In this paper, we report single-mode MgxZn1-xO based thin film resonators (TFRs) built on Si substrates. An acoustic mirror, composed of alternating quarter-wavelength silicon dioxide (SiO2) and tungsten (W) layers, is used to isolate the resonator from the Si substrate. High quality and well c-axis oriented MgxZn1-xO thin films are deposited on Si substrates using RF sputtering technology. X-ray diffraction (XRD) and field emission electron microscopy (FESEM) are used to characterize the MgxZn1-xO layers. The theoretical analysis of the TFR, based on the transmission line model, is presented. The BAW velocity and effective coupling coefficient of MgxZn1-xO can be tailored by varying the Mg composition in the films. The acoustic velocity increases with increasing Mg composition. The feasibility to use this structure to build ultra-high-sensitive mass BAW TFR sensor is analyzed. A mass sensitivity higher than 103 Hz cm2/ng is demonstrated.
Published in:	Proceedings of the 37th Annual Precise Time and Time Interval Systems and Applications Meeting August 29 - 31, 2005 Vancouver, Canada
Pages:	142 - 145
Cite this article:	Chen, Ying, Saraf, Gaurav, Wittstruck, Richard H., Emanetoglu, Nuri W., Lu, Yicheng, "Studies on MgxZn1-xO Thin Film Resonator for Mass Sensor Application," Proceedings of the 37th Annual Precise Time and Time Interval Systems and Applications Meeting, Vancouver, Canada, August 2005, pp. 142-145.
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