| Titre : | Design of a-IGZO Thin film transistors |
| Titre original: | a-IGZO تصميم ترنزيستور الشرائح الرقيقة |
| Auteurs : | Mohamed Labed, Auteur ; Noureddine Sengouga, 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. (141 p.) / 30 cm |
| Langues: | Anglais |
| Résumé : |
Thin film transistors (TFT) have received great attention due to their applications in flat planed display, e-paper and flexible electronics. a-IGZO based TFTs have shown superior performance as far the stability is concerned. However, some issues remain to be treated properly. In this thesis, numerical simulation (by SILVACO ATLAS) was carried out to three problems. The first, the effect of Hydrogen contamination of a-IGZO was investigated. It was found that donor defects near the valance band has no effect, while the mobility degradation induces a degradation in the TFT performance. Acceptor defects states near valance band is the reason of positive Vth shift. It is therefore concluded that near valance band defects are not donor defects but acceptor defects with a Gaussian distribution which can also degrade the mobility. The second, is the effect of different gate dielectrics. Four different insulators (SiO2 Si3N4, Al2O3 and HfO2) are examined. It is found that the output performance is significantly enhanced with high relative permittivity of the insulator. The HfO2 gate insulator gives the best performance: lower threshold voltage 0.23V and subthreshold 0.09 Vdec-1, and higher field effect mobility 13.73 cm2 s-1 V-1, on current and Ion/Ioff ratio 2.81 × 10−6 A,5.06 × 1012 respectively. Therefore, The HfO2 gate insulator showed high stability compared with other gate insulators materials. The third is a comparison of simulation to measurement of ultra-thin channel on the TFT performance. The thinner channel layer was found to have a better performance than the thicker channel layer. The 4 nm-thick, ultra-thin a-IGZO TFT exhibited high saturation mobility (7.56 cm2 V−1 s−1), low threshold voltage (2.73 V), a small value of sub threshold swing (0.22 Vdec−1) and a high on/off ratio (1.77 × 108). It was also noticed that the threshold voltage (Vth) shifts negatively as the thickness increases. The 4 nm long channel TFT shows more stability under NIBS and PBS while 16 nm have a strong degradation under NIBS and PBS |
| Sommaire : |
Abstract I Résumé II ملخص ......... III Table of Contents . .. IV List of Figures ........................................... VIII List of Tables XII General introduction ............................................................ References .. 4 Chapter I History and physics of thin film transistors ... 8 I.1 Introduction 8 I.2 History of thin film transistors 8 I.2.1 Field effect device .............................................................. 8 I.2.2 TFT based on a - Si: H and poly crystal Si ................................................... 10 I.2.3 Organic TFT .................................................... 12 I.2.4 Transparent Oxide Semiconductors TFT ..................................... 13 I.3 Physics and modeling TFTs .................................. I.3.1 Ideal MIS Capacitor structure.......................................... 16 I.3.2 Gate bias and threshold voltage ........................... 21 I.3.3 MOSFET operation ............................................ 22 I.3.4 Current-Voltage modulation .....................26 I.4 Thin film Transistor 28 I.5 References 30 Chapter II a-IGZO thin films transistors ................................. 34 II.1 Introduction 34 II.2 IGZO properties 35 II.2.1 Atomic structure .................... 35 II.2.2 Electronic structure of oxide..................... 36 II.2.3 Band structure .................. II.2.4 Origin large Electron mobility in AOS ................................... 39 II.2.5 Optical properties of a-IGZO ..................................... 41 II.2.6 Defect levels in IGZO................................................. 43 II.3 Growth a-IGZO thin films by sol-Gel ......................... 46 II.3.1 Spin coating ............................................................. II.4 Characterization a-IGZO thin films ..................................... 50 II.4.1 X-Ray Diffraction characterization ............ 50 II.4.2 UV-VIS Spectroscopy ........................................ 52 II.5 Fabrication a-IGZO TFT .............................. II.5.1 TFT structure ............................................. II.5.2 TFT process fabrication ............................... 57 TFT characteristics and performance indexes .................... 59 II.6.1 I-V characteristics ......................... II.7 References 63 Chapter III Simulation and fabrication of a-IGZO thin film transistors ....... 66 III.1 Introduction 66 III.2 Simulation IGZO thin film transistors ................................. 66 III.2.1 Fundamentals of Device Simulation ........................................ 67 III.2.2 Simulation by SILVCO TCAD .................................... 70 III.2.3 Commands File .......................... 71 III.3 Fabrication of thin film transistors by solution process ............................9 III.3.1 Cleaning 79 III.3.2 Deposition a-IGZO thin films........................................... 79 III.3.3 Electrode deposition ................................ 81 III.4 References 82 Chapter IV Results and discussion ................ 83 IV.1 Introduction 83 IV.2 TFT Structure and physical model ...................... 83 IV.3 Effect of deep defects on the performance of amorphous indium gallium zinc oxide thin film transistor 86 IV.3.1 Near valance band defects ........................................ 89 IV.3.2 Effect of the electron mobility .......................................... 96 IV.4 Simulation the influence of the gate dielectrics in amorphous indium-gallium-zinc oxide thin film transistors reliability ................. IV.4.1 TFT Structure ............................................ 98 IV.4.2 The effect of insulator on operation a-IGZO TFTs ..................... 99 IV.4.3 Impact of insulators on TFTs Vtch degradation .......................... 105 IV.4.4 Effect of fixed charge in HfO2 insulator: ........... 109 IV.4.5 Effect of HfO2 thi..................... 110 IV.5 Numerical simulation on thickness dependency and bias stress test of ultrathin IGZO thin-film transistors by a solution process ..................... 111 IV.6 Deposition a-IGZO thin films by sol gel method ...................... 124 IV.7 References 126 Conclusion ............................... 133 Appendix: Publications and Conferences .......... 135 |
| En ligne : | http://thesis.univ-biskra.dz/id/eprint/4629 |
Disponibilité (1)
| Cote | Support | Localisation | Statut |
|---|---|---|---|
| TPHY/94 | Théses de doctorat | bibliothèque sciences exactes | Consultable |
