薄膜式表面聲波元件之製作與分析

Study and fabrication of thin film SAW devices

吳德春(Te-Chun Wu)

指導教授 ： 高慧玲

中原大學/工學院/電子工程研究所/碩士(2002年)

https://doi.org/10.6840/cycu200200530

摘要

中文摘要
表面聲波元件(SAW)因其輕、薄、短、小和省電等功效已在通訊產業中佔重要地位。為降低表面聲波元件之製作成本，提高頻率使用範圍，及配合矽製程使SAW元件能與傳統電路整合(integrated)，因此開發出高波速且能與標準矽製程作整合的薄膜式表面聲波元件(Thin-film SAW devices)殊為重要。
氮化鋁(AlN)薄膜因其擁有良好的壓電特性與較高的聲波傳遞速度，再加上易與標準半導體製程作整合，因此我選擇氮化鋁薄膜作為研製薄膜式表面聲波元件之壓電材料。本實驗採用迴旋共振濺鍍系統(Helicon Sputtering System)於SiO2/Si基板上沉基單一排向與高平整度之氮化鋁薄膜，並利用XRD繞射分析與AFM來分析薄膜品質。在取得高品質的氮化鋁薄膜之後，我們利用傳統微影蝕刻之製程技術在其上製作指叉電極，以製成薄膜式表面聲波濾波器，並量測元件特性，探討薄膜製程與SAW元件特性之關係。
於本研究中我們成功的利用迴旋共振濺鍍系統所提供的低壓放電效果(1 mTorr)在SiO2/Si基板上沉積高排向(002)與高平滑度之氮化鋁薄膜，並建立其成長機制之模型。此外，在氮化鋁薄膜上製作表面聲波元件也有初步結果。我們發現氮化鋁薄膜的表面聲波波速在4500m/s左右，並不會隨著薄膜厚度有太大的改變，且表面聲波濾波器的插入耗損(insertion loss)會隨著薄膜厚度的增加而減少。此結果顯示氮化鋁薄膜式表面聲波元件與矽製程整合之可行性。

關鍵字

氮化鋁 ； 迴旋共振濺鍍系統 ； 表面聲波元件

並列摘要

Abstracts
This thesis researches the deposition of the piezoelectric film to fabricate the SAW devices on non-piezoelectric substrates. The main target is to investigate the process compatible with Si technology. Due to the excellent piezoelectricity, high surface acoustic wave velocity, substantial electromechanical coupling coefficient and good temperature stability, AlN films has been considered as an attractive thin film piezoelectric material for fabrication of on-chip surface acoustic wave (SAW) devices. I devoted to study the deposition of high AlN thin films and the fabrication of AlN SAW devices.
In this thesis, the AlN thin films were deposited on SiO2/Si by Helicon sputtering system. This sputtering method was able to sustain the plasma in a gas atmosphere of 10-4 Torr, and, in turn, to improve the surface morphology of the film. The preferred oriented c-axis AlN films on SiO2/Si have been obtained successfully under the growth parameters substrate temperature of 400℃, discharge pressure of 0.75mTorr, R.F. power of 150W, coil power of 50W and Ar/N2 ratio of 1. The optimized films exhibits extremely smooth surface with r.m.s. roughness of 3.2 Å.
The AlN SAW filters were demonstrated in this thesis. The phase velocity of SAW was determined from the relationship Vp=fc×λ, where fc is the center frequency of the transducers, and corresponded to an acoustic velocity of 4500 m/s. The results showed that insertion loss decreased with increasing the AlN film thickness. These results explored the possibility for thin film SAW devices incorporated into microwave integrated circuits.

並列關鍵字

AlN ； Helicon sputtering ； SAW devices

參考文獻

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