臺灣博碩士論文加值系統

本論文研究目標為以氮化鋁鈧研製3.5 GHz固態微型諧振器及濾波器，旨在透過鈧的摻雜使元件之有效機電耦合係數提高。本研究以鉬及二氧化矽做為高、低聲阻抗薄膜，於矽基板上堆疊成布拉格反射器；再以射頻磁控濺鍍系統將氮化鋁鈧壓電薄膜沉積於布拉格反射器上，透過調變濺鍍壓力、濺鍍功率及氮氣比例(N2/N2+Ar)等製程參數，尋求氮化鋁鈧薄膜c軸優選取向之最佳化特性；最後鍍上金屬上電極，形成諧振器及濾波器元件。
本研究透過調整對應諧振頻率之壓電薄膜厚度後，成功研製出一諧振頻率為3.46 GHz之SMR元件，符合所設定諧振頻率3.5 GHz之誤差範圍內，且Return loss為-30.62 dB及機電耦合係數為2.26%；另外，為了改善諧振器之頻率響應特性，將諧振器以不同退火溫度進行退火處理，結果顯示SMR元件之頻率響應皆獲得改善，其中以退火溫度700℃對元件的頻率響應改善最佳。為了進一步驗證氮化鋁鈧壓電薄膜對聲波元件特性之影響，本研究再行設計3.5 GHz之SMR濾波器元件，並成功製作出一中心頻率為3.44 GHz之SMR濾波器元件，符合所設定中心頻率3.5 GHz之誤差範圍內，並具有Insertion loss -17.2 dB、3 dB頻寬48 MHz。
本研究綜合元件特性分析之結果，以氮化鋁為壓電薄膜所製作之SMR元件的機電耦合係數約在1%左右，而以氮化鋁鈧薄膜製作出之SMR元件則擁有較佳之機電耦合係數2.26%，可證明於氮化鋁薄膜內摻雜鈧，確實有助於提升薄膜之機電耦合係數。

The 3.5 GHz solidly mounted resonator (SMR) and filter are fabricated using AlScN thin films, due to its high electromechanical coupling coefficient. In this study, the SiO2/Mo multilayered thin films with low and high acoustic impedances are used to consist the Bragg reflectors on Si substrates. Onto the Bragg reflectors, AlScN thin films are deposited using an RF magnetron sputtering system. In order to investigate and obtain the highly (002) c-axis oriented piezoelectric AlScN thin films, various sputtering pressures, sputtering powers and gas ratios (N2/N2+Ar) are varied to improve the crystalline characteristics. Finally, the top metal electrodes are deposited to obtain the solidly mounted resonators (SMRs) and filters.
After adjusting the thickness of the piezoelectric film corresponding to the resonant frequency, this study has successfully developed an SMR device with a resonant frequency of 3.46 GHz, which was within the error range of 3.5 GHz and had a return loss of -30.62 dB and an electromechanical coupling coefficient of 2.26%. In order to improve the frequency response of the resonator, the resonator was annealed at different temperatures. The results showed that the frequency responses of the SMRs were improved after annealing, among them, the frequency response of the SMR was optimal at the annealing temperature of 700°C. To further verify the effectiveness of AlScN piezoelectric thin films on the characteristics of acoustic devices, this study designed another 3.5 GHz SMR filter and successfully fabricated with a center frequency of 3.44 GHz, an insertion loss of -17.2 dB and 3dB bandwidth of 48MHz.
According to the analysis of the characteristics of the fabricated devices in this study, the electromechanical coupling coefficient of the SMR made of aluminum nitride (AlN) was about 1%, whereas the SMR made of aluminum nitride scandium film had a better electromechanical coupling coefficient of 2.26%. It could be demonstrated that the doping of scandium in the aluminum nitride film did contribute to the improvement of the electromechanical coupling coefficient of the piezoelectric film.

目錄

論文審定書 i
摘要 iii
Abstract iv
目錄 vi
圖目錄 ix
表目錄 xi
第一章 前言 1
1.1 研究背景 1
1.2 薄膜體聲波諧振器簡介 2
1.3 研究動機 5
1.4 研究內容 8
第二章 理論分析 9
2.1 鉬(Molybdenum, Mo)結構與特性 9
2.2 二氧化矽(Silicon dioxide, SiO2)結構與特性 9
2.3 氮化鋁(Aluminium Nitride, AlN)結構與特性 9
2.4 氮化鋁鈧 12
2.5 反應性濺鍍製備氮化鋁鈧薄膜 12
2.6 壓電理論 13
2.6.1 壓電效應 13
2.7 薄膜沉積原理 15
2.8 濺鍍原理 16
2.8.1 輝光放電 16
2.8.2 磁控濺鍍 17
2.8.3 射頻濺鍍 18
2.8.4 反應性濺鍍 18
2.9 快速熱退火(Rapid Thermal Annealing, RTA)製程 20
2.9.1 快速熱退火原理 20
2.9.2 快速熱退火製程對於薄膜結晶性之影響 21
2.10 SMR的理論 21
2.10.1 SMR特點 22
2.10.2 SMR的基本設計 22
2.11 SMR的參數性質 26
2.11.1 品質因子Q量測 26
2.11.2 機電耦合係數 量測 26
2.12 T型濾波器 27
第三章 實驗方法與步驟 28
3.1 實驗流程 28
3.2 基板清洗 28
3.3 元件設定之參數 30
3.4 SMR以及T型濾波器的製作流程 31
3.4.1 SMR製作流程 31
3.4.2 T型濾波器製作流程 32
3.5 直流與交流濺鍍系統與薄膜沉積 33
3.6 反應性射頻濺鍍系統與薄膜沉積 38
3.7 黃光微影製程 39
3.8 薄膜之特性分析 41
3.8.1 掃描式電子顯微鏡(Scanning electron microscopy, SEM) 41
3.8.2 X光繞射(X-Ray Diffraction, XRD) 41
3.8.3 原子力顯微鏡(Atomic Force Microscopy, AFM) 42
3.8.4 能量分散分析儀(Energy Dispersive Spectrometer, EDS) 42
3.9 快速熱退火(Rapid Thermal Annealing, RTA) 43
3.10 元件訊號量測 43
第四章 結果與討論 44
4.1 反射層的探討 44
4.1.1 高聲阻抗層鉬之最佳濺鍍參數 44
4.1.2 低聲阻抗層SiO2之最佳濺鍍參數 45
4.2 壓電層的探討 46
4.2.1 濺鍍壓力之影響 46
4.2.2 氣體分率之影響 49
4.2.3 濺鍍功率之影響 52
4.2.4 不同濺鍍條件之成份分析 55
4.3 SMR元件之頻率響應特性 57
4.4 SMR元件之退火處理 60
4.5 SMR元件之T型濾波器 62
第五章 結論 63
參考資料 64

圖目錄

圖1-1 FBAR元件之三種不同型態：(a)面蝕型、(b)背蝕型及(c)堆疊型 4
圖1-2 不同壓電材料之壓電係數(d33)與居禮溫度關係圖 5
圖1-3 ScxAl1-xN薄膜隨鈧摻雜濃度之(a)XRD分析圖及(b)壓電係數d33變化 6
圖1-4 鈧摻雜濃度對於ScxAl1-xN薄膜晶向成長之影響。(a~d) ScxAl1-xN薄膜之TEM剖面結構圖，(e~h) hexagonal相及cubic相之TEM結構分析示意圖；Sc摻雜濃度(a, e) 41%、(b, f) 42%、(c, g) 43%、(d, h) 45%
7
圖2-1 AlN的晶體結構 : (a)單位晶胞、(b)變形四面體結構、(c)纖鋅礦立體結構示意圖 10
圖2-2 壓電效應示意圖 : (a)正壓電效應，(b)逆壓電效應 14
圖2-3 薄膜沉積原理 16
圖2-4 直流輝光放電結構與電位分布圖 17
圖2-5 磁控濺射結構圖 18
圖2-6 反應式濺射示意圖 19
圖2-7 快速熱退火處理過程示意圖 21
圖2-8 波長為λ/2之SMR 24
圖2-9 波長為λ/4之SMR 25
圖3-1 SMR電極示意圖 31
圖3-2 T型階梯式濾波器電極示意圖 32
圖3-3 直流磁控濺鍍系統 35
圖3-4 射頻磁控濺鍍系統 36
圖3-5 射頻磁控濺鍍系統操作流程圖 37
圖3-6 舉離法流程圖 40
圖3-7 AlN之JCPDS 42
圖4-1鉬薄膜最佳濺鍍參數之表面粗糙度分析圖 45
圖4-2二氧化矽薄膜之表面粗糙度分析 45
圖4-3 不同濺鍍壓力下成長氮化鋁鈧薄膜之XRD圖 47
圖4-4 不同濺鍍壓力下成長氮化鈧鋁薄膜之表面及剖面形貌圖；(a) 10 mTorr、(b) 20 mTorr、(c) 30 mTorr 48
圖4-5 不同氮氣比例下成長氮化鈧鋁薄膜之XRD圖 50
圖4-6 不同氮氣比例下成長氮化鈧鋁薄膜之SEM表面及剖面形貌圖；(a) 20 %、(b) 50 %、(c) 80 % 51
圖4-7 不同濺鍍功率下成長氮化鈧鋁薄膜之XRD圖 53
圖4-8 不同濺鍍功率下成長氮化鈧鋁薄膜之SEM表面及剖面形貌圖；(a) 200 W、(b) 250 W、(c) 300 W 54
圖4-9 不同濺鍍條件下成長氮化鋁鈧薄膜，其薄膜內含鈧量之變化圖；(a)不同濺鍍壓力、(b)不同通入氮氣比例、(c)不同濺鍍功率 56
圖4-10 壓電薄膜厚度為863 nm之SMR元件頻率響應 58
圖4-11 調整壓電薄膜厚度後之SMR元件S11頻率響應 58
圖4-12 調整壓電薄膜厚度後之SMR元件S21頻率響應 59
圖4-13 不同退火溫度對SMR元件頻率響應之影響 61
圖4-14 3.5 GHz SMR濾波器頻率響應圖 62

表目錄

表1-1 壓電材料特性表 2
表2-1 AlN的材料基本特性表 11
表2-2 λ/2及 λ/4之SMR元件 22
表3-1 材料聲波特性表 30
表3-2 鉬薄膜沉積參數 34
表3-3 二氧化矽薄膜沉積參數 34
表3-4 氮化鈧鋁薄膜之最佳濺鍍參數 39
表3-5 RTA實驗製程參數 43
表4-1 不同濺鍍壓力下成長氮化鋁鈧薄膜之繞射峰角度 47
表4-2 SMR元件S21訊號比較 59

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