摘要：表面聲波元件(Surface Acoustic Wave Device)具有高性能、尺寸小、低成本，且與IC製程技術相容等優點，使其在電子工業與通訊系統上佔有很重要的地位。隨著行動通訊的日新月異及對於高資料傳輸速度的要求，傳統結構的表面聲波元件因受限於電極線寬與基底材料，已不敷使用，而層狀表面聲波元件能利用不同結構的搭配來提供多重的優點，以應付日益嚴苛的要求，因此本計畫擬以三年時間研製先進層狀表面聲波振盪器並建立相關的量測技術。計劃第三年以壓電層狀晶體波傳理論為基礎，配合格林函數及有效介電常數探討溫度效應對ZnO/Diamond/Si層狀表面聲波傳之影響，並計算ZnO/Diamond/Si層狀表面聲波機電耦合係數，實驗部分則進行ZnO/Diamond/Si層狀表面聲波濾波器之製作與量測。
Abstract: A vast market exists for surface acoustic devices (SAW) in areas such as wireless communication and a variety of sensor applications. For example, in the current mobile phone industry, the demand for SAW devices has led to a commercial market with a respectable level in annual sale. The manufacturing process of SAW devices is very closely related to that of IC process. Proper combinations of Taiwan’s IC industry with the R&D of SAW related devices may lead to a prosperous cost-effective market for Taiwan in the next one or two decades.
The utilization of surface acoustic wave (SAW) in the electronic filter and analog signal processing was started by White and Voltmer in 1965. Initially, the applications was focused on the large-volume low-cost market for IF filters for TV receivers and the low-volume high-cost SAW chirp filters in radar signal processing for military demands. It was not until the last decade, cost effective and large volume of SAW devices are needed due to the rapidly growing of wireless communication. As for the SAW research, a lot of literatures have come out since the end of 1970's. They include the selection of best cut for SAW propagation in the piezoelectric crystal, the design and modeling of the Interdigital transducers (IDT), study on the secondary effect, etc. In the recent years, propagation of surface waves in layered structures has been of interest in the development of dispersive SAW devices. By including a high velocity diamond layer between a piezoelectric layer and a Si substrate, the surface wave velocity can be increased significantly. This results to the increase of SAW frequency without decreasing the electrode spacing into the sub-micron region. In addition, layered SAW also preserves the advantages of high coupling coefficient and tiny temperature coefficient.
In this project, both the theoretical analyses and the experimental measurements of a layered SAW device will be conducted. In the first phase, to grasp the salient features of SAW design, a simple IF SAW filter will be designed and fabricated. In the second phase of this project, frequency response of a layered SAW device will be analyzed and discussed. In addition, inverse determination of thin film elastic properties by using the IDT SAW generation will be studied. Finally, a ZnO/Diamond/Si layered SAW will be fabricated and tested. This includes the calculations of the temperature effects, as well as the electromechanical coupling.
layered SAW filter
piezoelectric wave propagation