Title Page
ABSTRACT
국문 초록
PREFACE
Contents
NOMENCLATURE(OR LIST OF SYMBOLS) 17
CHAPTER 1. INTRODUCTION 19
CHAPTER 2. EXPERIMENTAL 21
CHAPTER 3. ELECTRICAL CHARACTERISTICS ANALYSIS OF IGZO TFTS 24
3.1. Electrical parameters of IGZO TFTs using a HfO₂ double layer as the gate insulator 24
3.2. Element bonding analysis of IGZO and HfO₂ 26
3.3. Hydrogen concentration analysis of HfO₂ thin films 30
3.4. HfO₂ surface roughness depending on reactant gases 32
3.5. Variation of crystallization lattice structure related to carbon concentration 33
3.6. On-Off current ratio of a-IGZO TFTs with different reactant gases 37
3.7. Mobility variation of a-IGZO TFTs with different reactant gases 38
CHAPTER 4. BIAS STRESS ENDURANCE OF IGZO TFTS WITH A HFO₂ DOUBLE LAYER GATE INSULATOR 39
4.1. Threshold voltage (VTH) shift during positive bias stress[이미지참조] 39
4.2. Mechanism of abnormal threshold voltage shift under positive bias stress 42
4.3. Time dependence of △VTH analysis during positive bias stress[이미지참조] 44
CHAPTER 5. SHORT-CHANNEL EFFECT OF IGZO TFTS WITH A HFO₂ DOUBLE LAYER GATE INSULATOR 47
5.1. Variations of the DIBL coefficient of IGZO TFTs 47
5.2. Transmission line model (TLM) analysis of the IGZO TFTs 50
CHAPTER 6. CONCLUSION 53
REFERENCES(OR BIBLIOGRAPHY) 54
Table. 1. Summary of electrical parameters: μsat, S.S, VTH, ION/OFF, and NT of IGZO TFTs with the double layer gate insulator for different ALD reactant gases.[이미지참조] 25
Table. 2. Summary of electrical parameters (at L=5 μm, W=100 μm, VG=4V): RC, rch, LT with the double layer gate insulator for different ALD reactant gases.[이미지참조] 51
Figure. 1. Schematic diagram of the IGZO TFTs with (a) single ALD-deposited HfO₂(using O₃ reactant) gate insulator (25 nm) and (b) double layer HfO₂(using O₃ reactant)/HfO₂(using... 22
Figure. 2. Transfer characteristics (IDS-VGS) of the IGZO TFTs for varied thicknesses utilizing different ALD reactant gases.[이미지참조] 24
Figure. 3. (a)-(d) O1s XPS spectra of the IGZO thin films that were produced on various gate insulators utilizing different ALD reactant gases. Schematic diagram of XPS... 26
Figure. 4. (a)-(d) O1s XPS spectra of various HfO₂ gate insulators utilizing different ALD reactant gases and schematic diagram of the XPS measurements sample. Schematic... 28
Figure. 5. Depth profiles of H- from HfO₂/IGZO stack with different ALD reactant gases using TOF-SIMS analysis. 30
Figure. 6. (a)-(d) Surface roughness of HfO₂ thin films using different ALD reactant gases. 32
Figure. 7. (a)-(d) HRTEM images of the HfO₂ thin films for various thicknesses utilizing different ALD reactant gases. 33
Figure. 8. Depth profiles of C-from HfO₂/IGZO stack with different ALD reactant gases using TOF-SIMS analysis. 35
Figure. 9. Transfer characteristics (IDS-VGS) of IGZO TFTs with different gate insulators under positive gate bias stress (PBS): (a) HfO₂(using O₃ reactant) 25 nm, (b) HfO₂(using O₃...[이미지참조] 40
Figure. 10. Time dependence of △VTH with different gate insulators during PBS tests. The measured data indicates that they are fitted for the stretched-exponential model or...[이미지참조] 44
Figure. 11. Variations of the DIBL coefficient (at L=5 μm, W=100 μm) for different gate insulators: (a) HfO₂(using O₃ reactant) 25 nm, (b) HfO₂(using O₃ reactant) 24 nm /... 48
Figure. 12. Total resistance of the IGZO TFTs for varied channel length with different gate voltages. 50