臺灣博碩士論文加值系統

氧化鋅由於其極佳的壓電特性，及其易於利用濺鍍法沉積於各種基板上的特性，近年來廣泛地被選取為成長壓電性薄膜的材料。而康寧7059玻璃基板，由於其熱膨脹係數與氧化鋅單晶相近似，所以被選為成長氧化鋅薄膜時的基板。
在環境控制中，可靠的氣體與濕度的感測正變的越來越重要。不同種的材料基於其導電係數會隨著與不同的吸附氣體產生氧化還原反應而改變，已被廣泛地用於氣體及濕度的偵測中。這些半導體材料中，氧化錫由於它對低濃度的氣體及濕度(百萬分之一等級)有很高的靈敏度，故很常被使用於偵測氧化/還原氣體。
本研究的目的乃在利用高週波磁控濺鍍法成長高品質及具有優選方向性的氧化錫與氧化鋅薄膜及其濕度感測的應用。在本研究中，我們的目標是製備一個表面聲波(SAW)濕度偵測器。首先，我們利用高週波磁控濺鍍法沉積氧化鋅薄膜於康寧7059玻璃基板上。然後，利用光蝕刻法及舉昇技術製備交趾狀電極於其上，以得到氧化鋅薄膜的表面聲波延遲線結構。最後，利用高週波磁控濺鍍法沉積氧化錫薄膜於氧化鋅表面聲波延遲線上，並量測此表面聲波濕度偵測器之各種特性及探討其靈敏度，響應時間等因素之影響。

Zinc Oxide, which has strong piezoelectric effect and can be sputtered on a variety of substrates, is a natural choice as the piezoelectric film layer in recent years. The Corning 7059 glass substrate, whose thermal expansion coefficient is nearly equal to that of ZnO single crystal, is usually chosen as the substrate for ZnO thin film.
Reliable gas and humidity detectors are becoming of great importance in environment control. A variety of materials have been used for gas and humidity sensing based on its conductivity changes produced by the oxidation and reduction of adsorbed gas. Tin Oxide (SnO2), one of these semi-conducting materials, is very widely used for sensing oxidizing/reducing gases due to its high sensitivity to small concentrations of gas (at p.p.m. level).
The goal of this preliminary research is to obtain high quality and preferred-oriented SnO2 and ZnO films by RF magnetron sputtering for their humidity sensing applications. Firstly, we deposit the ZnO film on Corning 7059 glass substrate by RF magnetron sputtering. Secondly, we use the photolithographic and the lift-off process to fabricate the inter-digital transducer (IDT) on this piezoelectric layer and get a ZnO film SAW delay line structure. Thirdly, we deposit a thin layer of SnO2 on the ZnO film SAW delay line. Finally, we will measure this SAW humidity sensor, and discuss its sensitivity, response time, etc.

Contents
Abstract (in Chinese) Ⅴ
Abstract (in English) Ⅵ
Acknowledgments Ⅶ
Contents Ⅷ
List of Figures ⅩⅡList of Tables ⅩⅦ
CHAPTER 1 Introduction 1
CHAPTER 2 Background Topics 5
2.1 Introduction 5
2.2 Piezoelectricity 6
2.3 Technique of Depositing Piezoelectric Films 9
2.4 Elucidation of SAW 12
2.5 Characterization of ZnO Thin Film SAW Devices 14
2.5.1 Insertion-loss 14
2.5.2 Phase velocity and coupling coefficient 15
2.6 Gas Sensor Based on SAW Property 16
2.7 Summary 20
CHAPTER 3 Growth and Evaluation of ZnO Layer
on Al/glass and Glass Substrates by RF
Planar Magnetron Sputtering 21
3.1 Introduction 21
3.2 Deposition of ZnO Films on Glass Substrate 23
3.2.1 Corning 7059 glass substrate cleaning procedures 23
3.2.2 Influence of deposition parameters 24
3.2.3 ZnO deposition 26
3.3 Deposition of ZnO films on Al/glass substrate 28
3.4 Evaluations of ZnO films 30
3.4.1 Evaluation of ZnO film grown on glass substrate 30
3.4.2 Evaluation of ZnO film on Al/glass substrates 35
3.5 Summary 37
CHAPTER 4 Fabrication and Characterization of
SAW Device 39
4.1 Introduction 39
4.2 The SAW properties of ZnO/Corning 7059 glass structure 40
4.2.1 Motivation 40
4.2.2 Results and discussions 41
4.2.2.1 Phase velocity 41
4.2.2.2 Coupling coefficient 41
4.3 IDT Fabrication Process 44
4.3.1 IDT design parameters 44
4.3.2 Photolithographic process 44
4.4 Evaluation of SAW properties of ZnO films on Corning
7059 glass substrate 50
4.5 Summary 53
CHAPTER 5 Growth And Evaluation of
Tin Oxide Thin Films by
RF Magnetron Sputtering 54
5.1 Introduction 54
5.2 Deposition of SnO2 Films on ZnO/glass Substrate 55
5.2.1 Deposit SnO2 films on glass substrate 57
5.2.2 Deposit SnO2 films on ZnO/glass structure 58
5.3 Evaluations of SnO2 Films 60
5.3.1 Effect of temperature for SnO2 deposition 60
5.3.1.1 X-ray diffraction analysis for SnO2 films at
different temperatures 60
5.3.1.2 Thickness measurement of SnO2 films at
different temperatures 65
5.3.1.3 SEM photograph of SnO2 films at
different temperatures 65
5.3.2 Effect of RF input power for SnO2 deposition 68
5.3.2.1 X-ray diffraction analysis for SnO2 films
with different RF input power 68
5.3.2.2 Thickness measurement of SnO2 films with
different RF input power 73
5.3.2.3 SEM photograph of SnO2 films with different
RF input power 73
5.3.3 Effect of oxygen pressure for SnO2 deposition 76
5.4 Summary 80
Chapter 6 Characterization of SAW Humidity Sensor
and Experiment Results 83
6.1 Introduction 83
6.2 The Fabricating Procedure of SAW Humidity Sensor 84
6.3 Experimental Results and Discussion 87
6.4 Summary 90
Chapter 7 Conclusions 92
References 95

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