| Titre : | Study of thin film transistors (TFTs) based on In, Sn and Zn amorphous oxides alloys |
| Titre original: | Etude des Transistors couches minces (TFTs) à base d'alliages des oxydes amorphes d'In, Sn et Zn |
| Auteurs : | Taki Eddine Taouririt, Auteur ; Afak Meftah., Directeur de thèse |
| Type de document : | Thése doctorat |
| Editeur : | Biskra [Algérie] : Faculté des Sciences Exactes et des Sciences de la Nature et de la Vie, Université Mohamed Khider, 2019 |
| Format : | 1 vol. (149 p.) / 30 cm |
| Langues: | Anglais |
| Résumé : |
This work is mainly focused on a numerical optimization of a-ITZO TFT based on the gate dielectric materials. Different types of high-k gate dielectrics are proposed. The effect of the thickness of : the double-layered dielectric, the equivalent oxide and the mono-layered dielectric of the gate is also presented. In addition, the effect of the interfacial states that can subsist between the TFT channel and the gate dielectric is also studied, for first low-k dielectrics such as SiO2 and second for high-k dielectrics such as Al2O3. Accurate analyses were implemented through numerical simulation of the device by Silvaco Atlas software that was used to carry out a detailed numerical analysis for investigating the relationship between these different effects and the performance and reliability of the device. The results showed that replacing the low-k SiO2 layer by a high-k dielectric layer in TFT based on the mono-layered dielectric leads to attractive improvements in the performance of a-ITZO TFT similar to the improvements resulting from the decrease in the physical thickness of the gate dielectric without the associated leakage effects. Also, the TFT device based on the double-layered dielectric (SiO2/HfO2) with a higher thickness (DDT = 70 nm) it can provide the same electrical properties that are offered by TFT device based on the equivalent oxide with a less thickness, almost seven times (EOT = 10 nm), without the associated leakage effects, while provides electrical properties better than properties that are offered by TFT based on the mono-layered dielectric (SiO2), for the same thickness (MDT = 70 nm). In addition, the TFT device based on the double-layered dielectric (Al2O3/HfO2) with a physical thickness (PT = 30 nm) it can provide good electrical properties better than the properties provided by TFT based on the double-layered dielectric (SiO2/HfO2) for the same physical thickness. However, it we cannot neglect the fundamental role of the interfacial low-k SiO2 layer between the channel and the high-k dielectric, which has some beneficial qualities with regard to the carrier mobility in the transistor channel. Also, although there is a difference in the value of leakage between the two devices, its effect is very poor on the performance of the device and its reliability, especially for low gate tensions. |
| Sommaire : |
GENERAL INTRODUCTION 15 CHAPTER I: a-ITZO TFT overview I.1 Introduction 10 I.2 The density of states (DOSs) for amorphous semiconductors 10 I.3 The a-ITZO in the In2O3-SnO2-ZnO System 14 I.4 Thin film transistors (TFTs) 18 I.4.1 History of TFTs 18 I.4.2 TFT structure 21 I.4.3 Output parameters 23 I.5 Low-k dielectric materials 27 I.6 High-k dielectric materials 30 I.7 Quantum mechanical tunneling and gate leakage ………… I.8 Equivalent oxide thickness of the mono-layer dielectrics I.9 Equivalent oxide thickness of bi-layer gate dielectrics References 40 CHAPTER II: Silvaco Atlas for TFT simulation II.1 Introduction 58 II.2 Amorphous semiconductors and defect states 58 II.3 The nature of the physically-based simulation 69 II.4 Atlas inputs and outputs 60 II.5 Transport models II.5.1 Drift-diffusion transport model 61 II.5.2 Advanced energy balance transport model 62 II.6 The order of Atlas commands 63 II.6.1 Structure specification 64 II.6.1.1 Mesh 64 II.6.1.1.1 WIDTH parameter in MESH statement 65 II.6.1.1.2 Mesh definition 66 II.6.1.2 Region 67 II.6.1.2.1 REGION definition 67 II.6.1.2.2 Specifying regions and materials 67 II.6.1.3 Electrode 69 II.6.1.3.1 ELECTRODE definition 69 II.6.1.3.2 Specifying electrodes 69 II.6.1.4 Doping 71 I I.6.2 Material models specification 71 II.6.2.1 Material 71 II.6.2.1.1 Specifying material properties 72 II.6.2.1.2 Specifying unknown or defined materials in Atlas 72 II.6.2.2 Models 74 II.6.2.2.1 Defining material parameters and models 74 II.6.2.2.2 Models of the density of state (DOS) used in the simulation II.6.2.3 Contact 79 II.6.2.4 Interface 80 II.6.3 Numerical method selection 82 II.6.3.1 Method 82 II.6.4 Solution specification 83 II.6.4.1 Log 83 II.6.4.2 Solve 84 II.6.4.3 Load 85 II.6.4.4 Save 85 II.6.5 Results analysis 85 II.6.5.1 Extract 86 II.6.5.2 Tonyplot 86 References 87 CHAPTER III: Results and discussions III.1 Introduction 93 III.2 a-IGZO TFT VS a-ITZO TFT performance 93 III.3 Effect of high-k gate dielectrics 98 III.3.1 Device structure 98 III.3.3 Effect of the physical thickness of the gate dielectric 102 III.3.4 Effect of the effective thickness of the gate dielectric 104 III.4 Effect of bi-layer dielectrics 109 III.4.1 Device structure 112 III.4.2 Effect of equivalent oxide thickness (EOT) of the gate dielectric III.4.3 Effect of the oxide and interface states 121 III.5 Effect of the interfacial dielectrics 127 III.6 Effect of the leakage current 131 III.7 Conclusion 138 References 139 GENERAL CONCLUSION 147 |
| En ligne : | http://thesis.univ-biskra.dz/id/eprint/4370 |
Disponibilité (1)
| Cote | Support | Localisation | Statut |
|---|---|---|---|
| TPHY/75 | Théses de doctorat | bibliothèque sciences exactes | Consultable |
