| Summary: | 碩士 === 國立清華大學 === 奈米工程與微系統研究所 === 104 === This work implements single crystal X-cut thin film Lithium Niobate (LN) in order to achieve a high electromechanical coupling coefficient kt^2.of the shear horizontal acoustic plate wave (SH-APM) resonators. The design of the device is carried out by the Finite Element Method (FEM) that can simulate the frequency of the SH0 mode resonators and their mode shape, and we use their frequency response to calculate the coupling coefficient that would be compared with the theoretical analysis and numerical result of prior arts; then we can confirm the validation of our simulation approach. In literature, the resonator possesses a high coupling coefficient at SH0 mode using the X-cut Lithium Niobate, which becomes our target in this work. In the fabrication process, we obtain off-the-shelf single crystal X-cut Lithium Niobate dies and we are using surface micromachining technology to fabricate the resonators. We design two fabrication process flows using the limited academic process resources and test the feasibility of the fabrication process. This process is roughly divided into three parts; the first part is photolithography, primarily responsible for defining the electrodes and etching holes; the present process for fabrication uses two masks. The second part is Lithium Niobate etching process. The third part is to etch the silicon dioxide; thus we use the wet HF to release the thin film structure. This study successfully demonstrated measurement results of the piezoelectric resonator with quality factor of 60, the electromechanical coupling coefficient of 15.8%, and motional impedance of 28.5 kΩ, respectively.
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