Microcrystalline silicon based thin film transistors fabricated on flexible substrate Hanpeng Dong To cite this version: Hanpeng Dong. Microcrystalline silicon based thin film transistors fabricated on flexible substrate. Electronics. Université Rennes 1, 2015. English. NNT : 2015REN1S173. tel-02384928 HAL Id: tel-02384928 https://tel.archives-ouvertes.fr/tel-02384928 Submitted on 28 Nov 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. N° d’ordre : ANNÉE 2015 THÈSE / UNIVERSITÉ DE RENNES 1 sous le sceau de l’Université Européenne de Bretagne pour le grade de DOCTEUR DE L’UNIVERSITÉ DE RENNES 1 Mention : Electronique Ecole doctorale MATISSE présentée par Hanpeng Dong Préparée UMR-CNRS 6164 IETR Institut d’Electronique et de Télécommunications de Rennes UFR ISTIC Thèse soutenue à Rennes Intitulé de la thèse : le 25 septembre 2015 Microcrystalline devant le jury composé de : Yvan BONNASSIEUX silicon based Thin Professeur, Ecole Polytechnique Palaiseau / rapporteur Film Transistors François TEMPLIER Ingénieur HDR CEA-LETI MINATEC / rapporteur fabricated on Flexible Takashi NOGUCHI Professeur, Université Okinawa Japon / Substrate examinateur Lei WEI Professeur, Université South-East Nanjing Chine / examinateur Emmanuel JACQUES Maître de Conférences Université Rennes 1 / examinateur Tayeb MOHAMMED-BRAHIM Professeur Université Rennes 1 / directeur de thèse Table of contents Table of contents 1 Table of contents Introduction………………………………………………………………………………………7 Chapter 1 Microcrystalline silicon thin film transistors: Applications and technologies…..11 1. Introduction ................................................................................................................................ 12 2. Low temperature TFTs for display applications ........................................................................ 12 2.1 TFTs for liquid crystal display .......................................................................................... 12 2.2 TFTs for OLED ................................................................................................................. 15 2.3 Quantum-dot light emitting display (QLED) .................................................................... 17 3. TFTs for Flexible electronics .............................................................................................. 18 3.1 Flexible displays ............................................................................................................... 18 3.2 Flexible sensors ................................................................................................................. 20 3.3 RFID tags .......................................................................................................................... 21 4. Different flexible substrates ....................................................................................................... 22 4.1 The thin glass .................................................................................................................... 23 4.2 Flexible stainless steel foil ................................................................................................ 23 4.3 Paper substrate .................................................................................................................. 24 4.4 Plastics .............................................................................................................................. 24 4.5 Conclusion ........................................................................................................................ 25 5. State-of-the-arts of low temperature TFTs ................................................................................. 26 5.1 Organic thin film transistors ............................................................................................. 27 5.2 Oxide semiconductor thin film transistors ........................................................................ 29 5.3 Silicon thin film transistors ............................................................................................... 31 5.3.1 Amorphous silicon thin film transistors ................................................................. 31 5.3.2 Low-temperature polycrystalline silicon (LTPS) thin film transistors ................... 32 5.3.3 Microcrystalline silicon thin film transistors .......................................................... 34 2 Table of contents 6. Conclusion .................................................................................................................................. 38 References ...................................................................................................................................... 40 Chapter 2 Technologies for the microcrystalline silicon TFT fabrication…………………..51 1. Introduction ................................................................................................................................ 52 2. Deposition technologies and material properties for the realization of low temperature microcrystalline silicon thin film transistor ................................................................................... 53 2.1 Undoped and doped microcrystalline silicon .................................................................... 53 2.1.1 Deposition of undoped and doped microcrystalline silicon film ............................ 53 2.1.2 Material properties of undoped and doped microcrystalline silicon ...................... 55 2.1.2.1 Undoped microcrystalline silicon ........................................................................ 55 2.1.2.2 N-type doped microcrystalline silicon ................................................................. 58 2.2 Deposition of gate insulator .............................................................................................. 59 2.2.1 Silicon oxide deposited by sputtering ..................................................................... 60 2.2.2 Silicon oxide deposited by ECR-CVD ................................................................... 61 2.2.3 Alumina deposited by ALD .................................................................................... 62 2.2.4 Silicon nitride deposited by PECVD ...................................................................... 64 3. Technologies for thin film characterization ............................................................................... 65 3.1 Thickness measurement by profilometer ................................................................... 65 3.2 Roughness and morphologies measurement by AFM ............................................... 66 3.3 Scanning electron microscopy (SEM) .............................................................................. 67 3.4 Measurement of the electrical conductivity ...................................................................... 67 3.5 Measurement of the crystalline fraction of microcrystalline silicon by Raman spectroscopy ............................................................................................................................ 69 4. Fabrication of microcrystalline silicon thin film transistor ........................................................ 71 4.1 Preparation of substrate ..................................................................................................... 71 4.2 Deposition of undoped microcrystalline silicon used as TFT channel ............................. 71 3 Table of contents 4.3 Deposition of doped microcrystalline silicon ................................................................... 72 4.4 Definition of channel area (Mask 1) ................................................................................. 72 4.5 Definition of TFT geometry (Mask 2) .............................................................................. 73 4.6 RCA cleaning of the silicon surface ................................................................................. 73 4.7 Deposition of gate insulator .............................................................................................. 74 4.8 Gate insulator etching for source and drain contact (Mask 3) .......................................... 75 4.9 Deposition of aluminum and definition of source, drain and gate electrode. (Mask 4).... 76 5. Basic working principle and characterization of microcrystalline silicon TFTs ....................... 77 5.1 Basic working principle of TFTs ...................................................................................... 77 5.1.1 Linear regime .......................................................................................................... 78 5.1.2 Saturation regime .................................................................................................... 79 5.2 TFTs electrical characteristics .......................................................................................... 80 5.2.1 Transfer characteristics ..........................................................................................