雙模聲子晶體表面聲波共振器系統之研製

Design and Fabrication of a Dual Mode Phononic SAW Resonator System

葉珮羚(Pei-Ling Yeh)

指導教授 ： 吳政忠

國立臺灣大學/工學院/應用力學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201610093

摘要

本研究依據聲子晶體的頻溝特性，提出以二維聲子晶體反射柵極與週期性波導結構所組成的雙模表面聲波共振器，並進行相關之數值分析與微機電實驗製程。在雙模表面聲波共振器中具有兩種不同偏振方向的波傳模態：沿著x波傳方向為雷利波模態(於矢狀平面內偏振)；另一沿著y波傳方向為表面橫波模態(水平剪切偏振)。研究中利用有限元素法(finite element method, FEM)分析一維週期性指叉電極結構、二維週期性波導結構與聲子晶體之頻散關係。依據分析結果求得為達共振效果，聲子晶體與波導層及指叉電極間最適化距離。實驗方面以微機電製程製作表面聲波元件，採用電子束微影技術系統製作次微米級的指叉電極與聲子晶體結構。在以二維石英聲子晶體反射柵極之表面橫波共振器的實驗中，不但降低插入損耗(14dB)，並提高共振器之品質因子。研究結果顯示利用聲子晶體為反射柵極之技術可應用於表面聲波元件。

關鍵字

聲子晶體 ； 雙模共振器 ； 雷利波 ； 表面橫波 ； 微機電製程

並列摘要

Based on the band gap of phononic crystals (PCs), this thesis presents the design and fabrication of a dual-mode surface acoustic wave (SAW) resonator system with 2-D air/ST-cut quartz PCs as reflective gratings and 2-D periodic wave guiding grating layer on ST-cut quartz substrate. There are two types of SAWs operated in the dual-mode SAW resonator system. One is the Rayleigh wave (in-sagittal-plane polarized) mode along the x-direction and the other is the surface transverse wave (shear-horizontal polarized) mode along the y-direction. By using finite element method (FEM), the dispersion relations of 1-D periodic IDT electrodes, 2-D periodic wave guiding grating layer and phononic crystals are calculated. Furthermore, we optimize the distance from wave guiding grating layer and from the PCs to the electrodes, to achieve the resonant effect. The SAW devices were fabricated by using the microelectromechanical system (MEMS) technology. We utilize electron-beam lithography to make the sub-micrometer IDT electrodes and PCs. The result of the experimental dual-mode SAW resonator performance shows that the minimum insertion loss is 21.45 dB in the surface transverse wave (STW) resonator with 2-D air/ST-cut quartz phononic reflective gratings in the y-direction, which is lower 14 dB than that without the PCs (35.8 dB). The insertion loss decreases and the Q-factor is also enhanced. The results of this study may be applied to develop SAW devices with the reflective PC gratings.

並列關鍵字

Phononic crystal ； Dual-mode SAW resonator ； Rayleigh wave ； Surface transverse wave ； MEMS

參考文獻

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