Fabrication of AlGaN High Frequency Bulk Acoustic Resonator by Reactive RF Magnetron Co-sputtering System.

Yu-Chen Chang,Chien-Chuan Cheng,Ying-Chung Chen

doi:10.3390/ma14237377

Yu-Chen Chang, Chien-Chuan Cheng + Show 1 more

Open Access

https://doi.org/10.3390/ma14237377

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Abstract

In this study, aluminum gallium nitride (AlGaN) thin films are used as the piezoelectric layers to fabricate solidly mounted resonators (SMR) for high frequency acoustic wave devices. AlGaN film is deposited on a Bragg reflector, composed of three pairs of Mo and SiO2 films, through a reactive radio frequency (RF) magnetron co-sputtering system at room temperature. The optimized deposition parameters of AlGaN film have a sputtering power of 175 W for Al target, sputtering power of 25 W for GaN target, N2 flow ratio (N2/Ar + N2) of 60%, and sputtering pressure of 10 mTorr. The obtained AlGaN film has a smooth surface, uniform crystal grains, and strong c-axis orientation. The contents of Al and Ga in the AlGaN film, analyzed by energy dispersive X-ray spectroscopy (EDS) are 81% and 19%, respectively. Finally, the frequency response s11 of the obtained SMR device shows that the center frequency is 3.60 GHz, the return loss is about −8.62 dB, the electromechanical coupling coefficient (kt2) is 2.33%, the quality factor (Q) value is 96.93 and the figure of merit (FoM) value is 2.26.

Highlights

Wireless communication systems have been advanced to 4G and 5G
The acoustic wave devices used in wireless communication equipment have higher requirements, such as frequency response, kt2, Q, and figure of merit (FoM) [1,2,3]
The bulk acoustic wave device has lower insertion loss, higher frequency, and wider frequency band [4,5,6,7,8]; it is suitable for high frequency wireless communication system applications

Summary

Introduction

Wireless communication systems have been advanced to 4G and 5G. At the same time, the acoustic wave devices used in wireless communication equipment have higher requirements, such as frequency response, kt2, Q, and FoM [1,2,3]. The acoustic wave devices used in wireless communication equipment have higher requirements, such as frequency response, kt2, Q, and FoM [1,2,3]. The bulk acoustic wave device has lower insertion loss, higher frequency, and wider frequency band [4,5,6,7,8]; it is suitable for high frequency wireless communication system applications.

Results

Conclusion