Fabrication and characterization of bendable thin film transistors with a-Si:H and a-IGZO channels

다국어 초록 (Multilingual Abstract)

In this thesis, the bendable thin film transistors (TFTs) with hydrogenated amorphous silicon (a-Si:H) and amorphous indium gallium zinc oxide (a-IGZO) channels were fabricated on the plastic substrate and their mechanical and electrical characteristics under bending strain were investigated through experiment and simulation. In chapter 1, fundamental theories of bendable TFTs with a-Si:H and a-IGZO channels and the failure mechanism to mechanical strain were introduced. In chapter 2, experimental procedures for the fabrication of the bendable TFTs with a-Si:H and a-IGZO channels were described in detail. In chapter 3, the influence of overlapped gate region and various channel widths on the electrical characteristics of the bendable a-Si:H TFTs under bending stress are investigated by the mechanical simulation. In addition, effect of physical densification on sub-gap density of states distribution in a-IGZO film and the electrical characteristics of bendable a-IGZO TFTs as function of bending radius are discussed. In conclusion, the electrical characteristics of bendable TFTs with a-Si:H and a-IGZO channels and the mechanical analysis of bending stress exhibited possibilities for application in the bendable electronics including displays.

목차 (Table of Contents)

• 1. Introduction: Overview 1
• 1.1. Bendable TFTs 2
• 1.1.1. Basic Operation and Structure of TFTs 3
• 1.1.2. a-Si:H TFTs 8
• 1.1.3. a-IGZO TFTs 11
• 1.2. Mechanical Issues on Bending Deformation 17
• 1.2.1. Failure Mechanism 17
• 1.2.2. Substrate 23
• 2. Experimental Procedures 26
• 2.1. Fabrication of Bendable a-Si:H TFTs 27
• 2.1.1. Overlap Structure Between Gate and Source/Drain 27
• 2.1.2. Various Channel Widths of a-Si:H 31
• 2.2. Fabrication of Bendable a-IGZO TFTs 34
• 2.2.1. RF Sputtering Condition 34
• 2.2.2. Split Channels and Top-Gate Structure 36
• 3. Results and Discussion 39
• 3.1. Electrical and Mechanical Characteristics of Bendable a-Si:H TFTs 40
• 3.1.1. Effect of Overlap Between Gate and Source/Drain Regions 40
• 3.1.2. Effect of Channel Widths 50
• 3.2. Electrical Characteristics of Bendable a-IGZO TFTs 57
• 3.2.1. Effect of Physical Densification on Sub-gap Density of States 57
• 3.2.2. Effect of Split Channels and Top-gate Structure 64
• 4. Conclusions 74
• References 78