Direct Pattern Transfer of Meso- to Nanoscale Structures Using an Electrohydrodynamic Lithography = 전기수력학적 리소그래피를 이용한 마이크로 및 나노크기의 패턴 기술

다국어 초록 (Multilingual Abstract)

Direct write technologies are the most recent approaches to form fine patterns whose linewidths range from meso- to nanoscales. With a direct write approach, patterns or structures can be obtained directly without the use of variable fabrication processes, masks, and liquid for etching. Direct write technologies, therefore, are the low cost and environmental friendly processes. As one of the direct write technologies, electrohydrodynamic lithography (EHL) can be used to obtain meso- to nanoscale patterns onto a substrate. Electrohydrodynamic lithography makes use of an electrohydrodynamic film instability in which a thin liquid film can be destabilized by strong electric field, applied across two capacitor plates. Strong electric field can produce forces that overcome the surface tension in thin liquid films, including an instability that features a characteristic regular order. Pattern replication is also possible when a patterned substrate is used as a top capacitor plate. The advantage of using this electric field based technique is that (a) larger areas can be patterned in a parallel fashion, and (b) that a range of lateral length scales can be replicated in a single step.
In this work, inorganic material such as TiO2 and ZnO based inorganic resists are employed as a dielectric thin film and various shapes and sizes including ordered array patterns at micron and nanometer scales were replicated using an electrohydrodynamic lithography. The patterned structures were then heat treated at various temperatures to yield crystalline structures. X-ray diffraction, Field emission scanning electron microscopy, Photoluminescence, and Raman spectroscopy were used for structural characterizations and for the demonstration of its functionality. This method can be extended to other functional oxide systems and has a great potential as a cost-effective and large area pattern transfer technology.

목차 (Table of Contents)

• 1. Introduction 1
• 1.1 Motivation of the study 1
• 1.2 Our strategy 2
• 2. Theoretical Background 4
• 2.1 Lithography 4
• 2.1.1 Types of Resists 5
• 2.1.1.1 Organic based Resist 8
• 2.1.1.2 Inorganic based Resist 8
• 2.1.2 Lithography and its different Type 10
• 2.1.2.1 Photolithography 10
• 2.1.2.2 Electron Beam Lithography 13
• 2.1.2.3 Soft Lithography 14
• 2.2 Electro-Hydrodynamic Lithography (EHL) 16
• 2.2.1 Stability of Thin Films 19
• 2.2.1.1 Hydrodynamics 21
• 2.2.1.2 Surface Pressure 23
• 2.2.1.3 Laplace Pressure 24
• 2.2.1.4 Gravity 26
• 2.2.1.5 Van der Waals Pressure 26
• 2.2.1.6 Linear Stability Analysis 27
• 2.2.1.7 Dispersion Relation 28
• 2.2.2 Electrohydrodynamic Instability 30
• 2.2.2.1 Electrostatic Pressure 30
• 2.2.2.2 Characteristic Wavelength 32
• 3. Electrohydrodynamic Lithography System 34
• 3.1 Total System 34
• 3.2 Parts of EHL System 36
• 3.2.1 Manual Z-stage 36
• 3.2.2 Porous Chuck 36
• 3.2.3 Piezo Translator (PZT) 38
• 3.2.4 Capacitive Sensor 40
• 4. Experiments 44
• 4.1 Sample Preparation 44
• 4.1.1 Synthesis of Titanium Dioxide (TiO2) Precursor Resist 44
• 4.1.2 Making of TiO2 Thin Film 45
• 4.2 Heat Treatment of TiO2 Precursor film 47
• 4.3 Pattern Transfer with TiO2 Precursor Resist using EHL 48
• 4.3.1 Pattern Transfer with TiO2 Precursor Resist 48
• 4.3.2 Pattern Transfer with TiO2 Precursor Resist in Confined Regio 48
• 4.3.2.1 Electron Beam (E-beam) Lithography 49
• 4.3.2.2 Pattern Transfer in Confined Region 49
• 4.4 Pattern Replication with TiO2 Precursor Resist 51
• 4.4.1 Photolithography 51
• 4.4.2 Pattern Replication with TiO2 Precursor Resist 52
• 4.5 Synthesis of Hierarchical Structures Combined EHL with CVD 54
• 4.5.1 Pattern Transfer ZnO Precursor Resist 54
• 4.5.2 Growth of ZnO Nanowires on Patterns 55
• 5. Results and Discussion 58
• 5.1. Functionalization of TiO2 Precursor Resist 58
• 5.1.1 Crystal Structure of TiO2 58
• 5.1.2 Photoluminescence spectroscopy 60
• 5.1.3 X-Ray Diffraction (XRD) 62
• 5.1.4 Raman Spectroscopy 64
• 5.2 Pattern Transfer using TiO2 Precursor Resist 67
• 5.2.1 Pattern Formation of TiO2 Precursor Resist 67
• 5.2.2 Pattern Transfer of TiO2 Precursor Resist in Confined Region 69
• 5.2.2.1 Pattern of NiO Precursor Resist using E-Beam Lithography 69
• 5.2.2.2 Pattern Formation of TiO2 Precursor Resist in Confined Region 69
• 5.3 Pattern Replication with TiO2 Precursor Resist 72
• 5.3.1 Photolithography 72
• 5.3.2 Pattern Replication of TiO2 Precursor Resist 72
• 5.4 Hierarchical Structures of Zinc Oxide (ZnO) 75
• 5.4.1 Formation of Patterns of ZnO Precursor Resist 75
• 5.4.2 Synthesis of ZnO Nanowires on Patterns 75
• 6. Conclusions 78
• References 80
• ABSTRACT 84