| Summary: | 碩士 === 國立成功大學 === 電機工程學系碩博士班 === 90 === Abstract
This paper reports on a film type bulk acoustic wave resonator (FBAR) fabricated by lithography, dry etching and RF magnetron sputtering of aluminum nitride (AlN)films. The acoustic cavity is made by inductively coupled plasma (ICP) etched. The bottom and top electrodes are deposited by using RF magnetron sputtering. In this paper, the influence of AlN thickness on the frequency response of thin film bulk acoustic wave resonators (FBARs) with SiO2 and Si3N4 as the support membranes were investigated. The FBAR consists of a piezoelectric aluminum nitride (AlN) thin film and sandwiched between two aluminum thin film electrodes. All lie on thin films SiO2 and Si3N4 as support membranes onto silicon substrates. A range of 0.9μm, 1.8μm, 2.7μm, 3.6μm and 4.5μm AlN thin films thickness were deposited by reactive RF magnetron sputtering. The AlN thin film had a smooth surface and with highly c-axis oriented and well-aligned columnar. The result showed that the thicker AlN films of the resonator increased higher resonant frequency.
The crystallography of the coated films was analyzed by x-ray diffraction (XRD) and by operating the scanning electron microscope (SEM) for the film surface and cross-sectional properties. The fabricated FBAR is measured by network analyzer (HP 8753ES).
FBAR devices which consisted of 2.7μm AlN, 0.2μm bottom electrode, 0.18μm top electrode, and 0.2μm of SiO2 membrane have a resonant frequency of 2.855 GHz in this paper. The experiment also successfully demonstrated that reducing the bottom electrode thickness will increase the resonant frequency, so that it is possible to tune a FBAR device to a specific frequency by carefully control of AlN and electrode thickness.
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