Development of a film bulk acoustic resonator based on ZnO

作者：Tang Liang^*; Hao Zhen Hong; Qiao Dong Hai; Wang Cheng Hao

来源：Microfabrication Technology, 2008, (2): 57-60.

A film bulk acoustic resonator (FBAR) and its fabrication process were presented. Sputtered ZnO thin film was used as the resonator's piezoelectric layer, and its supporting membrane was formed by bulk-etching the silicon substrate from the backside. In order to avoid the wrinkling of the released membrane caused by the internal residual stress, SiNx/SiO2/SiNxmulti-layer support structure was introduced. The piezoelectric ZnO thin film was deposited by DC reactive magnetron sputtering. The X-ray diffraction measurement shows that the sputtered film is highly c-axis-oriented with a full width at half maximum (FWHM) 0.2273°. Its scanning electron microscopy (SEM) image shows the columnar structure is perpendicular to the smooth and dense film surface. The fabricated FBAR samples were tested using a HP 8753D network analyzer. The measurement results show that the resonator has strong thickness-extension (TE) vibration modes with fundamental resonance frequency at about 750 MHz and second harmonic resonance frequency at about 1.5 GHz. With the quality of ZnO piezoelectric film improved, the resonator could be used in RF oscillators and RF front-end filters.

• 出版日期2008