本文使用X-cut的鋰酸鈮(LiNbO3)壓電薄膜(Single crystal X-cut lithium niobate piezoelectric thin film)、二氧化矽、矽基板構成之LNOI結構作為研究的基礎，且全文的主軸在於用有限單元法(FEM)分析SH-SAW共振器(Shear Horizontal-Surface Wave Resonator)在不同LNOI、電極時的表現，並針對實驗結果進行探討與改善。第二、三章是SH-SAW共振器的研究過程，第四章介紹實驗的製程及結果分析，第五章是三次實驗的詳細過程與總結。本研究包含三次表面聲波共振器的製作與實驗結果。第一次實驗以100nm Au電極製作出的SH-SAW resonator具有24%的機電耦合係數和接近400的Q值(品質因數)。
為了改善Q值，查閱文獻發現鋁的Q值高於金，故本團隊於第二次實驗製程改採委外代工並更換電極的材料為鋁，但成品的金屬品質極差，元件的性能受到嚴重的破壞，故我們以數據後處理的方式還原出該元件原本的樣貌。我們利用構建等效電路模型來研究造成該次實驗失敗的因素，並萃取出共振器的各項參數。最後我們在改進製程後成功製作出以100nm 厚度的鋁金屬為電極的SH-SAW共振器，其具有600的Q值與16.7%的機電耦合係數。Q值與金電極的共振器相比有約1.5倍的提升，充分展現鋁金屬的潛能，本文的最後我們提出更進階的設計方法改善SH-SAW共振器的性能。

In this study, the LNOI structure composed of X-cut lithium niobate thin film, silicon dioxide thin film, and silicon substrate is used as the piezoelectric substrate for making surface acoustic wave (SAW) resonators. The performance of the shear horizontal SAW (SH-SAW) resonator is analyzed by finite-element method (FEM). Chapters 2 and 3 will introduce the numerical analysis of SH-SAW resonators in detail. Chapter 4 covers the fabrication processes and results. The experimental results are given in Chapter 5. Three batches of SH-SAW devices were fabricated separately in this study. The SH-SAW resonator fabricated with 100nm Au electrode in the first batch shows an electromechanical coupling coefficient of 24% and a quality factor close to 400.
In order to improve the quality factor, we outsourced the manufacturing and replaced the electrode material with aluminum in the second experimental process, but the metal quality of the final structure was extremely poor. The post-data analysis of this batch is used to recover the frequency response of the resonator in this batch. An equivalent circuit model is built to study the factors causing the failure of this batch, and it is used to extract the parameters of the resonator. Finally, after improving the process, we successfully fabricated SH-SAW resonators with 100nm-thick aluminum metal as the electrode, which show high quality factors up to 600 and electromechanical coupling coefficients up to 16.7%. At the end of this thesis, we propose a more advanced design method to improve the performance of SH-SAW resonators.

目錄
第一章 前言 ....................................................15
1-1 研究動機與背景 .............................................15
1-2文獻回顧 ....................................................18
第二章 LNOI SH-SAW基礎理論與頻散分析 ............................34
2-1壓電效應 ....................................................34
2-2壓電材料介紹 ................................................34
2-2-1 尤拉角(Euler Angles) .....................................36
2-3聲波壓電共振器原理 ...........................................37
2-3-1聲波種類介紹 ..............................................38
2-4 頻散分析 ...................................................42
2-4-1 晶體切割方向之選擇( X、Y、Z-cut ) .........................42
2-4-2 SH-SAW於不同HAL結構中之選擇 .................................43
2-4-3 hLN/λ之選擇 ..............................................44
2-4-4 電極材料及厚度之選擇 ......................................46
第三章SH-SAW元件設計 ...........................................49
3-1 設計概念 ...................................................49
3-1-1 指叉式電極 ................................................49
3-2 元件模擬 ...................................................52
3-2-1 模型邊界條件設定 ..........................................56
3-2-2 共振器指叉電極(IDT)數量對keff2的影響 .......................58
3-2-3 反射電極(Grating-Reflector, GR)數量對keff2的影響 ..........59
3-3 Modified Butterworth-Van Dyke 等效電路模型 ..................61
3-4 元件光罩設計 .................................................63
第四章 SH-SAW元件製程與結果 ......................................65
4-1 製程流程及參數 ..............................................65
4-2 製程瓶頸與解決方法 ..........................................68
4-2-1材料之間應力造成的裂痕 ......................................68
第五章 SH-SAW元件量測結果與討論 ..................................71
5-1 量測環境架設 .................................................71
5-2 100nmAu/0.7µmLN/0.7µmSiO2結構之量測結果與分析 ..................73
5-3 0.1µmAl/0.7µmLN/0.7µmSiO2 / 525µmSi結構之製程結果與元件參數萃取...79
5-4 0.1µm Al/ 0.7µmLN / 2µmSiO2 結構之量測結果與分析 .............97
第六章 結論與未來工作 ...........................................112
參考文獻 .........................................................114
附錄一、萃取鋁濕蝕刻速率實驗 .....................................116

[1] R. Ruby, P. Bradley, J.D.Larson, “PCS 1900 MHz duplexer using thin film bulk acoustic resonators (FBARS),” Electron. Lett., vol. 10, pp.794-795, May 1999.
[2] D. Morgan, “Surface Acoustic Wave Filters : With Applications To Electronic Communication And Signal Processing 2th ed,” Academic Press, US, June 2007.
[3] I.E. Kuznetsova; B.D. Zaitsev; S.G. Joshi; I.A. Borodina, “Investigation of acoustic waves in thin plates of lithium niobate and lithium tantalite,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control,vol.48,pp.322-328, Jan. 2001.
[4] S. Gong and G. Piazza, “Laterally vibrating lithium niobate MEMS resonators with high electromechanical coupling and quality factor,” in Proc., 2012 IEEE International Ultrasonic Symposium (IUS’12), Las Vegas, NV, USA, Oct. 2012, pp. 1051-1054.
[5] S. Gong and G. Piazza, “Monolithic Multi-Frequency Wideband RF Filters Using Two-Port Laterally.Vibrating Lithium Niobate MEMS Resonators,”J. Microelectromech. Syst., vol. 23, no. 5, pp. 1188-1197, Oct. 2014.
[6] Y.-H. Song and S.Gong, “Spurious mode suppression in SH0 lithium niobate laterally vibrating MEMS resonators,” in Proc., 2015 IEEE Electron Devices Meeting (IEDM’15), Washington, DC, USA, Dec. 2015, pp.18.5.1-18.5.4.
[7] Y. Song and S. Gong, “Wideband Spurious-Free Lithium Niobate RF-MEMS Filters,” J. Microelectromech. Syst., vol. 26, no. 4, pp. 820-828, Aug. 2017.
[8] J. Zou, V. Yantchev, “Ultra-Large-Coupling and Spuriou-Free SH0 Plate Acoustic Wave Resonators based on thin LiNbO3,” IEEE Electron Device Lett , vol.67, no. 2, pp. 374- 386, Feb. 2020.
[9] A.Kochhar,A. Mahmoud,“X-Cut Lithium Niobate-Based Shear HorizontalResonators for Radio Frequency Applications,” IEEE Electron Device Lett, vol 29, no 6, pp 1464-1467, Dec 2020.
[10] M. Kadota and S. Tanaka, “Improved quality factor of hetero acoustic layer (HAL) SAW resonator combining LiTaO3 thin plate and quartz substrate,” in Proc., 2017 IEEE International Ultrasonic Symposium (IUS’17), Washington, DC, USA, Sep. 2017, pp. 1-4.
[11] R. Nakagawa, H. Iwamoto and T. Takai, “Low Velocity I.H.P. SAW Using Al/Pt Electrodes for Miniaturization,” in Proc., 2019 IEEE International Ultrasonic Symposium (IUS’19), Glasgow, UK, Oct. 2019, pp. 2083-2086.
[12] T.-H. Hsu et al, “Large coupling acoustic wave resonators based on LiNbO3/SiO 2 /Si functional substrate,” IEEE Electron Device Lett, vol. 41, no. 12, pp. 1825-1828, Dec. 2020.
[13] T. Kimura, M. Omura, Y. Kishimoto and K. Hashimoto, “Comparative study of acoustic wave devices using thin piezoelectric plates in the 3–5-GHz range,” IEEE Trans. Microw. Theory Techn., vol. 67, no. 3, pp. 915-921, Mar. 2019.
[14] J. Rosenbaum, “Bulk acoustic wave theory and devices,” Artech House, UK, 1988.
[15] R. Lu, M.-H. Li, Y. Yang, T. Manzaneque, and S. Gong, “Accurate extraction of large electromechanical coupling in piezoelectric MEMS resonators,” J. Microelectromech. Syst., vol. 28, no. 2, pp. 209-218, Apr. 2019.
[16] T. Takai, “High-Performance SAW Resonator on New Multilayered Substrate Using LiTaO3 Crystal,” IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 64, no. 9, pp. 1382-1389, Sep. 2017.
[17] T.-H. Hsu, F.-C. Su, K.-J. Tseng and M. -H. Li, “Low Loss and Wideband Surface Acoustic Wave Devices in Thin Film Lithium Niobate on Insulator (LNOI) Platform,” in Proc., 2021 IEEE Micro ElectroMechanical Systems (MEMS’21), Gainesville, FL, USA, Jan. 2021, pp. 474-477.
[18] K.-J. Tseng and M.-H. Li, “Frequency and Coupling Factor Scaling of Shear Horizontal SAW Resonators in LNOI Platform,” in Proc., 2020 IEEE International Frequency Control Symposium and International Symposium on Applications of Ferroelectrics (IFCS-ISAF’20), Keystone, CO, USA, Oct. 2020, pp. 1-3.
[19] S. Zhang, “Surface Acoustic Wave Resonators Using Lithium Niobate on Silicon Carbide Platform,” in Proc., 2020 IEEE/MTT-S International Microwave Symposium (IMS’20), Los Angeles, CA, USA, Aug. 2020, pp. 253-256.