鑽石表面聲波濾波器之製作與特性分析

Abstract

鑽石表面聲波濾波器之製作與特性分析 研究生 : 管正平 指導教授 : 陳家富 博士 國立交通大學材料與工程研究所 摘要 在各種不同的CVD鑽石應用中，由於鑽石的高表面聲波傳遞速度,和即使是多結晶的鑽石膜，亦得以應用在表面聲波元件中，而且在鑽石膜厚上的要求，只需要幾個微米的厚度就足夠了，因為其能量都只集中在表面，所以能夠在低成本下大量地生產.。 想要到達GHz範圍內的高頻表面聲波元件，一般較傳統的表面聲波元件的材料例如石英、鈮酸鋰、鉭酸鋰是很難做到的。由於近幾年來CVD鑽石成長技術，我們可以來研究表面聲波元件在含有鑽石結構上的製作，而且這個結構和系統也已經可以實際應用在表面聲波濾波器上了。此外，鑽石的高熱傳導率和其優異的高彈性常數也被發現能夠用在超高功率控制方面，所以鑽石除了在高頻應用上的特性，比一般的傳統材料優秀外，甚至應用在低頻時，也比傳統材料勝出了許多。 在本研究中，我們成功的利用熱燈絲CVD法，在矽晶片成長了大面積的多晶鑽石膜，其厚度將近30毫米。而氧化鋅由於其極佳的壓電特性，及其易於利用濺渡法沉積於各種基板上的特性，近年來廣泛地被選取為成長壓電薄膜的材料。高均勻品質的鑽石膜結合上高優選方向的氧化鋅薄膜及利用舉離法所研製出的5毫米的交趾狀電極而製作出完美性能的鑽石表面聲波濾波器。 而且，我們還比較了在相同的交趾狀電極下，氧化鋅/鑽石/矽，以及氧化鋅/矽，這二種結構的表面聲波濾波器的特性差異。結果發現鑽石表面聲波濾波器在各方面的特性皆優於無鑽石薄膜者。詳細的流程及結果，都會列在本篇論文之中。 最後，我們也相信在未來的通訊系統之中，以鑽石為基材的表面聲波元件也將被會發現具有廣大的應用在高頻元件上。

Fabrication and Characterization Analysis of Diamond SAW Filter Student : Cheng-Ping Kuan Advisor : Dr. Chia-Fu Chen Institute of Materials Science and Engineering National Chiao Tung Unversity Abstract Amongst the varieties of applications of Chemical Vapor Deposition (CVD) diamond, the Surface Acoustic Wave (SAW) device using its high SAW velocity, is supposed to be one of the practical applications, because polycrystalline film can be utilized. And the thicknesses of only several microns are sufficient because the energy concentration is on the surface, which enables low-cost manufacturing. The SAW devices with a high frequency, on the GHz range, and which are hard to realize via SAW devices using conventional materials such as quartz, lithium niobate (LiNbO3), and lithium tantalate (LiTaO3). Due to the recent progress in CVD-diamond growth technology, we have studied SAW devices fabricated by structures with polycrystalline diamond. And it has been found that systems involving these materials are practical for high-frequency SAW filters. Moreover, the high thermal conductivity, as well as the high elastic constant, of diamond are found to enable super-high power-handing capabilities, which surpass the characteristics of conventional materials even at low frequency. In this work, we have been successfully developed the large areas of polycrystalline diamond on silicon by Hot Filament CVD (HFCVD). The thickness of diamond films are about 30µm. Zinc Oxide, which has strong piezoelectric effect and can be sputtered on a variety of substrates, is a nature choice as the piezoelectric film layer in recent years. High uniformity and quality of diamond films associated with highly preferred orientation ZnO thin film on above and the 5µm interdigital transducers (IDTs) fabricated by lift-off process exhibit wonderful performance of diamond SAW filters. Moreover we compare the structures of ZnO/Diamond/Silicon and ZnO/Silicon on the characteristics of SAW filters with the same interdigital transducers (IDTs). We found the Diamond SAW Filter was much better than the ZnO SAW Filter. The details and results will be presented in this thesis. And we believe that the SAW devices based on diamond will also find broad applications on high frequency devices in future communication systems. Keywords: SAW filter; HFCVD; Diamond; ZnO