臺灣博碩士論文加值系統

本篇論文乃採用射頻濺鍍磁控的方式濺鍍氮化鋁(AlN)薄膜，當然，要得到一優良的體聲波元件，薄膜的C-軸將成為使得元件表現良好的主要因素。由實驗的結果得到，要成長出良好的C-軸優良取向的沉積條件乃必須將機台的濺鍍條件四項可控變因設定為濺鍍功率350W、基板溫度400°C、氮氣/氬氣濃度比例為60：40、腔體內部壓力為4mtorr，另外將此薄膜做X-RD繞射以分析薄膜的晶向排列是否有C-軸存在、並且網路分析儀(Network Analysis)看出元件的操作頻率點的S參數大小以分析出此元件的表現特性是優或劣。此外，高頻體聲波元件的波導設計影響了功率訊號輸入到整個元件裡面的訊號是否足以讓元件震盪，故在設計元件的大小時，必須先將波導設計的線寬與形狀考慮在元件設計部分，此亦為本篇論文最精華的部分。在製作一顆高頻聲波元件時，我們必須先將主導整顆元件的一層壓電薄膜表現特性使其最佳化，亦即此薄膜具有C-軸優選指向，而這層薄膜最主要是由鋁(Al)原子和氮(N)原子所形成的化合物，我們稱之為氮化鋁(AlN)，此氮化鋁薄膜的晶向將會影響整顆高頻聲波元件頻率響應的優劣。隨著目前無線通訊(Wireless Communication)的發展，應用在不同資料通訊傳輸，將積體化的射頻濾波器(RF Filter)製造在矽晶體上需求量甚大，而此濾波器應用在無論是數位或是類比的高頻積體電路上都具有很多的優點，但是利用傳統的方法製造表面聲波濾波器與介電振盪器的射頻濾波器結構卻存在著很多困難的地方。故利用高頻FBAR濾波器很適合被做在射頻積體電路裡面，因為當此元件被做在矽基板上時，具有較低的插入損(Insert Loss)，也比表面聲波元件(SAW Device)濾波器更低。本論文使用了氮化鋁與鋁(Al)/[白金+鈦](pt/Ti)當成高頻FBAR元件的壓電薄膜和上電極與下電極，因為壓電薄膜具有兩個反射聲波的表面，致使聲波能量被限制在壓電薄膜中，而聲波能量在壓電薄膜裡的多次碰撞後，其聲波能量將會一直衰減到零為止。要製作一顆非常成功的高頻FBAR元件，其首要的條件乃必須成長出一層C-軸優選指向(002)的氮化鋁，要具有壓電特性的氮化鋁薄膜，必須將氮化鋁的晶格方向成長為優良的C-軸取向(002)，因為具有優良的C-軸取向，氮化鋁薄膜才會有良好的壓電特性，而至於如何讓氮化鋁具有優良的C-軸取向，亦為本章探討的重要課題之一。

This thesis is devoted to the discussion of aluminum nitride (ALN) which thin film deposition for BAW devices has the obvious C-axis direction is deposited by RF-Sputtering. The C-axis orientation of the aluminum nitride film will affect the high frequency bulk acoustic wave device performance. By the results of experiments, we find that if we want a perfect C-axis direction of thin aluminum nitride film, we must control four process parameters, mainly: the chamber pressure is 4m (torr), the substrate temperature is 400°C, the sputtering power is 350W and the percent of nitrogen in the process gas is 60%. We analyzed the binding energy, the chemical content of thin film by the X-RD and S parameter of the device with Network Analyzer. The design of the device input/output pads for the high frequency bulk acoustic wave device plays an important role, we have to consider the geometry of the wave guide line which effects the device. We have successfully deposited C-axis oriented ALN thin film and the preliminary measurement on the BAW device shows that the acoustic wave velocity for the ALN film obtained from the S parameter measurement is about 7000 m/sec, assuming to the factors contributed to the resonance frequency deviation. This result is about 70% of the ideal value.

第一章 簡介…………………………………………………………………1
第二章 氮化鋁之文獻回顧與體聲波元件理論分析……………………4
2-1壓電理論介紹…………………………………………………………4
2-2壓電效應………………………………………………………………4
2-3氮化鋁(AlN)薄膜內部晶格結構、特性、與其應用之簡介……………7
2-3-1氮化鋁內部晶格結構介紹………………………………………….7
2-3-2氮化鋁特性介紹…………………………………………………9
2-3-3氮化鋁應用………………………………………………………9
2-4成長薄膜晶向的物理沉積概念………………………………………….10
2-5影響氮化鋁薄膜C-軸(002)成長因素…………………………………11
2-6 FBAR體聲波元件設計與影響元件的外部效應………………………16
2-6-1製作長方形板…………………………………………………….16
2-6-2製作圓形板電極[6] …………………………………………….17
2-6-3製作電極越來越小的結果………………………………………18
2-6-4縮小電極，串聯共振頻率(fs)與並聯共振頻率(fp)和阻抗關係.......19
2-6-5 能陷原理………………………………………………………….20
2-6-6利用串聯共振頻率(fs)與並聯共振頻率(fp)得機電耦合係數( )20
2-6-7 質量加載效應…………………………………………………22
2-7網路分析儀的操作原理…………………………………………………22
2-8體聲波振盪器元件的Q值……………………………………………22
第三章 體聲波元件之光罩設計原理與其探討…………………..……29
3-1體聲波元件的光罩佈局與設計原則………………………………….…29
3-2四道光罩合起來的俯視圖…………………………………….…………33
3-2-1長方形FBAR元件重疊光罩圖………………………………………33
3-2-2圓形FBAR元件重疊光罩圖………………….………………………34
3-2-3高頻體聲波元件(FBAR)其Dummy Pad的光罩設計圖……………35
3-3體聲波振盪器元件(FBAR)之工作原理…………………………………36
3-4建立FBAR model與網路分析儀的port1與port2關係[8]: …………38
3-4-1建立FBAR的等效電路以便計算出各個電阻(R)、電感(L)、電容(C)
的值…………………………………………………………………39
3-4-2 由網路分析儀萃取出的S參數轉換為S參數的dB值……………..40
3-5體聲波元件內部聲波傳遞行為……………………………………….…41
第四章元件製作流程、薄膜分析、與製作完成圖…………………………...42
4-1元件製作流程與細節討論……………………………………………….42
4-2 X光繞射(X-Ray Diffraction)結果圖分析…………………………......…49
4-2-1 sample1的薄膜X光繞射分析…………………………………………51
4-2-2 sample2的薄膜X光繞射分析…………………………………………52
4-2-3 sample2的薄膜X光繞射分析…………………………………………53
4-2-4 sample4的薄膜X光繞射分析…………………………………………54
4-3 X-RD繞射圖結果討論……………...……………………………………55
4-4 成長C-軸取向氮化鋁薄膜實驗數據…………………………………57
4-5量測前的網路分析儀機台校準………………………………………61
4-5-1第一次元件測試結果、討論與元件未來設計之方向……………........61
4-5-2討論與解決元件的設計方向……….………………………………….62
4-6整個FBAR元件的改善……….………………………………………….63
4-6-1改善後的薄膜之C-軸優選指向….…………………………………….63
4-6-2改善後光罩設計.……………………………………………………….65
4-6-3整合以上三道光罩…………………………………………………......66
4-6-4元件之傳導線改良後製作完成圖……………………………………..67
4-6-5元件改善後之量測結果……………………………………………......68
第五章 結論與未來展望………………………………………...……......70
參考文獻……………………………………...……........................................71

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