本論文之目的在於研製可適用於高頻無線通訊及高感測度質量感測器之薄膜體聲波諧振器。本論文採用固態微型諧振器的結構，詳細探討此結構中之布拉格反射器與氮化鋁壓電層的研製方法，並且針對c軸傾斜氮化鋁、質量負載效應與體聲波諧振特性進行探討與分析。
對於布拉格反射層的研製方面，本論文採用三種材料組合，分別為AlN/Al、 Mo/Ti與Mo/SiO2，詳細探究材料之選擇與薄膜粗糙度對於頻率響應之影響。本研究發現，多層薄膜之表面粗糙度為主導聲波諧振響應之關鍵參數，可藉由材料的選擇與調變製程參數來研製平整度佳之布拉格反射器；其中，AlN/Al的組合由於其薄膜粗糙度過大，造成聲波能量散逸，無法達成良好之諧振；而Mo/Ti的組合可藉由適當之濺鍍參數成長出低粗糙度之布拉格反射器，達成良好之聲波諧振；最後，本研究採用高聲阻抗比之Mo/SiO2薄膜，其高低聲阻抗比可達4.7，而且七層之薄膜粗糙度可達2.2 nm，成功地研製出共振頻率為2.5 GHz之固態微型體聲波諧振器。
此外，本論文亦成功地研製出四分之一波長諧振模態之固態微型諧振器。相較於常見的二分之一波長諧振模態，本論文研製之元件具有較高之元件品質因素與較高之質量感測度。
為建構雙模態之聲波元件，本研究採用偏軸成長法研製c軸傾斜的氮化鋁薄膜，其聲波元件具有激發出縱向與剪向諧振的能力；此外，本研究利用質量負載效應來調變雙頻諧振器的頻率，探討負載效應對於頻率響應的關係；由實驗中發現，無論氮化鋁傾斜角的改變與負載質量的改變，縱波與剪波的諧振頻率皆維持著約為1.76倍的比例關係；並且發現負載質量的增加與頻率的偏移量並非為線性關係，進而提出一改良之Sauerbrey equation用以描述此非線性的變化。然而，隨著c軸傾斜的角度增大，縱向諧振的品質因素呈現下降之趨勢，為了改善此一現象，採用偏軸及傾斜基板之製程，改進c軸傾斜氮化鋁壓電薄膜所產生之縱向與剪向聲波，成功地獲得優異之雙頻率諧振響應。
本研究成功地獲得優異之雙頻諧振響應，對於頻率之負載效應亦有充分且完整之探討，所完成之固態微型體聲波元件對於高頻無線通訊以及高感度質量感測器有相當之應用價值。

The solidly mounted resonator (SMR) is constructed of a Bragg reflector and a piezoelectric layer AlN. In order to obtain an appropriate SMR for the high frequency communication applications and high sensitivity bio-sensor applications, the Bragg reflector, the AlN, and the loading effect have been investigated thoroughly.
The thesis presents the influences of surface roughness of the Bragg reflector and materials’ selection on the resonance characteristics of an SMR. Three combinations of thin films, AlN/Al, Mo/Ti, and Mo/SiO2, are adopted. Originally, an AlN/Al multi-layer is used as the Bragg reflector. The poor surface roughness of this Bragg reflector results in a poor SMR frequency response. To improve the surface roughness of Bragg reflectors, a Mo/Ti multi-layer with a similar coefficient of thermal expansion is adopted. By controlling deposition parameters, the surface roughness of the Bragg reflector is improved. Finally, a material combination of Mo/SiO2 with high acoustic impedance ratio of 4.7 is adopted. Better resonance characteristics of SMR are obtained. The experimental results show a distinct resonance phenomenon around 2.5 GHz and excellent noise restraint.
Afterwards, a ¼λ mode SMR is experimentally realized. The selection of high and low acoustic impedance for the first layer beneath piezoelectric layer results in the ¼λ mode and ½ λ mode resonance configurations, respectively. The coupling coefficient Keff2 of 6.9% is obtained, which is in agreement with the theoretical analysis.
Following, the theoretical analysis upon the dual mode frequency-shift was characterized, and a modified formula was carried out. The c-axis tilted angle of AlN was altered as well as the various mass loading on the SMR. Based on the experimental results, the dual resonance frequencies showed a nonlinear decreasing trend with a linear increase of the mass loading. Furthermore, the ratio of the longitudinal resonant frequency to the shear resonant frequency remained at a range around 1.76 despite the various c-axis tilted angles of AlN and gradual mass loading on the SMR. The electromechanical coupling coefficient, keff2, of the shear resonance rose with the increase of the c-axis tilted angle of AlN. However, the longitudinal resonance fades away with the AlN c-axis tilted angle, and the quality factor of the longitudinal resonance decreases.
Finally, the dual mode resonances are improved by tilting the off-center substrates toward the sputtering source and successfully enhance the longitudinal resonance while preserve the shear resonance at the same time. Not only the shear resonance for the liquid-based sensing application, but also an outstanding longitudinal resonance could be obtained. The practicability of the dual-mode resonator is extended for the applications of high frequency wireless communication and high sensitivity bio-chemical sensors.

摘要 I
ABSTRACT III
TABLE OF CONTENTS V
FIGURE AND TABLE CAPTIONS VII
CHAPTER 1 INTRODUCTION 1
CHAPTER 2 THEORETICAL ANALYSIS 5
2.1 PIEZOELECTRICITY 5
2.2 ANALYSIS OF THE SMR 7
2.2.1 Types of Bragg reflector 7
2.2.2 Analysis of transmission line equation 8
2.2.3 The effective electromechanical coupling coefficient, Keff 10
2.2.4 The quality factor, Q 10
2.3 MASS SENSOR APPLICATION 11
2.4 MATERIALS CHARACTERISTICS 14
2.4.1 The characteristics of AlN 14
2.4.2 The characteristics of aluminum 15
2.4.3 The characteristics of Mo 16
2.4.4 The characteristics of Ti 16
2.4.5 The characteristics of SiO2 17
2.5 REACTIVE MAGNETRON SPUTTERING TECHNIQUE 18
2.5.1 Sputtering 18
2.5.2 Glow discharge 19
2.5.3 RF Magnetron sputtering 20
2.5.4 c-axis tilted texture by RF Magnetron sputtering 20
CHAPTER 3 EXPERIMENTAL PROCEDURE 22
3.1 THE CLEANING OF SUBSTRATES 22
3.2 SPUTTERING SYSTEM AND THIN FILM DEPOSITION 23
3.2.1 RF magnetron sputtering system 23
3.2.2 Thin film deposition of piezoelectric layer 24
3.2.3 DC magnetron sputtering system 25
3.2.4 Thin films deposition of Bragg reflectors 25
3.3 LOADING MASS 26
3.4 PHOTOLITHOGRAPHY 27
3.5 FABRICATION PROCESSES OF THE SMR DEVICE 28
3.6 X-RAY DIFFRACTION (XRD) ANALYSIS 29
3.7 SCANNING ELECTRON MICROSCOPY (SEM) ANALYSIS 29
3.8 ATOMIC FORCE MICROSCOPY (AFM) ANALYSIS 29
3.9 FOURIER TRANSFORM INFRARED SPECTROMETER (FTIR) ANALYSIS 30
CHAPTER 4 RESULTS AND DISCUSSION 31
4.1 INVESTIGATION OF BRAGG REFLECTORS 31
4.1.1 Selection of Bragg reflectors 31
4.1.1.1 Combination of AlN/Al 32
4.1.1.2 Combination of Mo/Ti 33
4.1.1.3 Combination of Mo/SiO2 35
4.1.2 Sequence and number of layers 37
4.1.2.1 The effect of sequence of layers 37
4.1.2.2 The effect of number of layers 38
4.1.3 Optimum fabrication parameters 39
4.1.4 Key factors for fabricating Bragg reflectors 40
4.2 INVESTIGATION OF ALN 42
4.2.1 Investigation of a highly c-axis oriented AlN 42
4.2.2 Investigation of a c-axis tilted AlN 43
4.2.3 Improvement of a c-axis tilted AlN 45
4.3 INVESTIGATION OF LOADING EFFECT 47
4.3.1 The Sauerbrey equation and the frequency modulation 47
4.3.2 The modified Sauerbrey equation 48
4.3.3 Loading effects on the c-axis tilted AlN 50
4.3.4 The key factors for the loading effect 51
CHAPTER 5 CONCLUSION 53
5.1 Influence of the surface roughness and the selection of material combinations of Bragg Reflectors on resonance characteristics of the SMRs 53
5.2 Fabrication and frequency response of SMRs with ¼λ mode configuration 54
5.3 BAW Properties on the dual mode frequency shift of SMRs 54
5.4 An improvement of tilted AlN for shear and longitudinal acoustic wave 55
CHAPTER 6 FUTURE WORKS 56
REFERENCES 57
APPENDIX A PUBLICATION LIST 124
APPENDIX B AUTOBIOGRAPHY 126

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