臺灣博碩士論文加值系統

Metal films are widely used in radio-frequency microelectromechanical system capacitive switches. The mechanical properties of bulk materials have been extensively investigated in the literature. However, the mechanical behavior of thin metal films used in microelectronics and mechanical microdevices has yet to be explored in detail. Besides, the mechanical behavior in thin metal films is likely to differ from that in the bulk material. In this study, therefore, a fatigue test was performed and analyzed to evaluate the influence of composition on the mechanical properties of metal films.
Specifically, aluminum-magnesium alloy free-standing films with proximate composition were fabricated by means of DC magnetron sputtering, UV lithography, and wet etching. In particular, the mechanical properties of aluminum-magnesium alloys thin films with various magnesium contents in the range of 0–10 wt.% under cyclic tensile loading are investigated. The membranes were pressurized up to 105 times, during which their stress and strain states are continuously recorded. Mechanical properties diagrams were elaborated and examined at various testing variables. The results of this study serve to compare and evaluate the most optimal thin film in several compositions, and thus it can potentially completely replace the aluminum thin film in the future for capacitance switches.

TABLE OF CONTENTS
ACKNOWLEDGMENTS i
Abstract ii
TABLE OF CONTENTS iii
LIST OF FIGURES vi
LIST OF TABLES x
1. Introduction 1
1.1. Background information 1
1.2. Research motivation 5
2. Literature review 7
2.1. Thin-film fabrication and mechanical properties 7
2.1.1. Thin-film deposition methods 7
2.1.2. Thin-film mechanical properties 10
2.2. Bulge test of thin film 14
2.2.1. Experimental techniques for thin-film fatigue testing 18
2.2.2. Fatigue in free-standing thin films 20
2.2.3. Fatigue in thin films on a substrate 21
2.2.4. Failure modes and damage in thin films 21
2.2.5. Face-centered cubic metals 23
2.3. Elasticity 24
3. Experimental Description 25
3.1. Specimen preparation 25
3.2. Fabrication of aluminum-magnesium alloy thin films 25
3.2.1. RCA cleaning 27
3.2.2. Deposited silicon nitride film 28
3.2.3. Photolithography 30
3.2.4. Inductively coupled plasma dry etching of silicon nitride film 33
3.2.5. Wet etching of wafers 34
3.2.6. Deposited aluminum-magnesium alloy thin films 38
3.3. Bulge testing 42
3.3.1. Introduction of the bulge measurement technique 42
3.3.2. Theoretical calculation and theory for stress and strain measurement 43
3.3.3. Experimental setup 48
3.3.4. Pressure controller measurement 50
3.3.5. Data acquisition 52
3.3.6. Position sensing detector 54
3.3.7. Vacuum chamber design and introduction 59
3.3.8. Monotonic bulge test 61
3.3.9. Fatigue testing of thin film 62
4. Results and discussion 65
4.1. FESEM morphology analysis 65
4.1.1. Surface morphology observation 65
4.1.2. Analysis of the surface composition of energy-dispersive X-ray spectroscopy 67
4.2. Mechanical properties of aluminum-magnesium alloy thin films 69
4.2.1. Bulge pressure-displacement curve 69
4.2.2. Bulge stress-strain curve conversion 71
4.2.3. Discussion of Young’s coefficient 73
4.2.4. Discussion of residual stress 73
4.3. The fatigue analysis of aluminum-magnesium alloy thin films 74
4.3.1. Mechanical properties change in thin films 74
4.3.2. Effect of magnesium content on fatigue behavior 76
5. Summary and Conclusion 77
6. References 79

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