高品質氮化鋁薄膜及其表面聲波元件之研製

The Study of AlN Thin Film Deposition and Surface Acoustic Wave Devices

吳至軒(Chih-Hsuan Wu)

指導教授 ： 高慧玲

中原大學/工學院/電子工程研究所/碩士(2001年)

https://doi.org/10.6840/cycu200100160

摘要

隨著高頻無線通訊產業的蓬勃發展，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有重要地位。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)，因此開發出擁有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)殊為重要。
壓電薄膜的選擇與品質對於薄膜式表面聲波元件效能與結果有著決定性的影響，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(5600-6000m/s)再加上其易與標準半導體製程做整合，因此在眾多壓電材料的選擇當中我們選擇氮化鋁(AlN)薄膜作為我們研製薄膜式表面聲波元件之壓電材料。在本研究中將採用迴旋共振濺鍍系統(Helicon Sputtering System)於SiO2/Si基板上沉積單一排向與高平滑度之高品質氮化鋁薄膜，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表面聲波元件之製程技術致力於薄膜式表面聲波元件之開發。
在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(1mTorr)於SiO2/Si基板上沉積出高排向(002)與高平滑度(3.2Å/(2μm)2)之氮化鋁薄膜，並觀察其它沉積條件與薄膜結晶排向的關係以建立成長機制之模型。此外，也在氮化鋁薄膜上製作表面聲波元件並有初步結果。此結果為薄膜式表面聲波元件與IC製程的整合技術帶來了極大的可能性。

關鍵字

氮化鋁 ； 迴旋共振濺濺鍍系統 ； 表面聲波元件

並列摘要

We research 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. Among many kinds of piezoelectric materials, we choose AlN films because of its high surface acoustic wave velocity (5600-6000 m/s) and excellent piezoelectricity. Generally speaking, preferred orientation and smooth surface are the key factors of AlN SAW devices. Therefore, we devoted to deposit high quality AlN thin films and fabricate 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. In our experiments, the CPW method to measurement this thin film SAW is better than Microstrip Line because the effect of the vertical E-field. The center frequency of SAW filter was 880 MHz and the calculated acoustic wave velocity was 8800 m/s. These results explored the possibility for thin film SAW devices incorporated into microwave integrated circuits.

並列關鍵字

Helicon sputtering system ； SAW devices ； AlN

參考文獻

1. Ju-Won Soh, Won-Jong Lee: ”SAW Characteristic of AlN Films Deposited on Various Substrates using ECR Plasma Enhanced CVD and Reactive RF Sputtering”, IEEE Ultrasonics Symposium, 1996, P.299-302.

2. H. Ming Liaw: ”The Characterization of Sputtered Polycrystalline Aluminum Nitride on Silicon by Surface acoustic Wave Measurements”, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol. 42, No. 3. 1995, P.404-409.

3. Hwan-Chul Lee and Ki-Young Lee: “Effect of Hydrogen Addition on the Preferred Orientation of AlN films Prepared by Reactive Sputtering”, Thin Solid Films, Vol. 271, 1995, P.50-55.

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