A simple and cost-effective post-lithography solution to reduce the critical dimensions of structures on the nanometer scale using an external mechanical force without any modification of the existing exposure system is proposed by this work. This study presents a tunable aluminium (Al) wire grid polarizer (WGP) on polyethylene naphthalate (PEN) substrate fabricated by the laser interference lithography (LIL) built on 325 nm exposure system. The characteristic pitch of WGP achieves a further 18% post-exposure shrinkage which is also reflected on improved TM (transverse magnetic) to TE (transverse electric) ratio by 33% with a defined operation window and specified optimized region of strain. The simulations in this study prove the rise of the extinction ratio with the modulation of the WGP pattern. Physical evidence explains fall of the extinction ratio for mainly the increase of the metal crack volume.

Chapter 1 Background and Motivation 1
1.1 Introduction 1
1.2 Background 2
1.2.1 Dimensional (Critical Dimension – CD) Shrinkage in Nano-Lithography 2
1.2.1.1 Moore's Law 2
1.2.1.2 Conventional Ultra-Violet (UV) Lithography 3
1.2.1.3 Extreme Ultra-Violet Lithography (EUVL) 4
1.2.1.4 Enlarging of Numerical Aperture (NA) – Immersion Lithography 7
1.2.1.5 Low-k1 Lithography 9
1.2.1.6 Photoresist Treatment 10
1.2.1.7 Double Patterning 11
1.3 Strain and Critical Dimension Shrinkage 13
1.3.1 Strain process 13
1.3.2 Poisson's Ratio and its Relation to CD 17
1.4 Polarizers 18
1.4.1 Definition of Polarizer 18
1.4.2 Performance Factors of Polarizers 19
1.4.2.1 Extinction Ratio 19
1.4.2.2 Contrast Ratio 19
1.4.2.3 Transmittance 19
1.4.2.4 Working Region of Polarizers 19
1.5 Wire Grid Polarizer 20
1.5.1. Conical Grating Wire Grid Polarizer 21
1.5.2 Imbedded wire grid polarizer for the visible spectrum 21
1.5.3 Double sided wire grid polarizer 22
1.5.4 Broadband wire grid polarizer for the visible spectrum 22
1.5.5 Corrosion resistant wire-grid polarizer 23
1.6 Fabrication Methods of Wire Grid Polarizers 24
1.6.1 Nanoimprint Lithography 24
1.6.2 Fabrication by Electron Beam (e-beam) Lithography (EBL) 26
1.6.3 Focused Ion Beam Lithography (FIB) 27
1.6.4 Dip-pen Nanolithography (DPN) 29
1.6.5 AFM Nano-scribing (scanning probe techniques) 30
1.6.6 Stencil Lithography (Shadow Mask Lithography) 32
1.6.7 Nanoskiving 34
1.6.8 Interference Lithography (IL) 36
Chapter 2 Simulation and Design 41
2.1 Structure Overview and Simulation 41
2.1.1 Structural Overview 41
2.1.2 Simulation of the WGP's Critical Dimensions 42
2.1.2.1 Influence of Pitch to the Optical Performance of the WGP 42
2.1.2.2 Influence of Thickness 43
2.1.2.3 Influence of the Duty Cycle 45
2.2 Selecting the Best Design of WGP 46
2.2.1 Grating to Substrate Interface 46
2.2.1.1 Adhesion of the Metal to Substrate 46
2.2.1.2 Design with consideration of material Poisson's ratios 48
Chapter 3 Fabrication Process of WGP 50
3.1 Material Selection 50
3.1.1 Substrate 51
3.1.2 Material Selection of the Metal Grating for WGP 57
3.2 Pre-fabrication steps 60
3.3 Enabling the Tunability of the WGP 61
3.4 FDTD Simulation of Strained WGP 65
3.4.1 Surface crack ratio 66
3.4.2 Strained WGP Simulation 69
3.5 Equipment for Measurements and Process 71
Chapter 4 Results and Discussion 74
4.1 SEM, AFM Results and the Extinction Ratio Measurements 74
4.2 Surface Crack Ratio and Crack Formation 81
4.2.1 Surface Crack Ratio 81
4.2.2 Study of Adhesion and Delaminations 84
Chapter 5 Discussion 86
5.1 Conclusion 86
5.2 Future Work 87
References 88

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