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Electronique CMOS en silicium microcristallin sur substrat flexible transparent

Abstract : The aim of this thesis is to fabricate both types of microcrystalline silicon TFTs N and P (Thin Film Transistors) on flexible and transparent substrate. The microcrystalline silicon technology was optimized in our laboratory at low temperature <180°C. The flexible and transparent chosen substrate is PEN Q65FA (Polyethylene naphthalate) produced by DuPont Teijin Film. N-type microcrystalline silicon top-gate TFTs are successfully fabricated on PEN. These N-TFTs are fairly uniform and replicable. Likewise, N-TFTs are stable under gate bias stress of +15V, the VTH shift was only 12% during four hours. Furthermore, P-TFTs are demonstrated on PEN, the characteristics of these P-TFTs are adequate and they need further work. Both types of these TFTs are mechanically solicited. Tensile and compressive strains were applied by bending TFTs with different curvature radius varying between infinite (flat) and 0. 5 cm. Electron mobility increases (40%) with tensile strain and decreases with compressive one. In contrast, hole mobility decreases with tensile strain and increases (27%) with compressive one. This behaviour is mainly due to the variation of silicon properties. TFTs work until a radius of 1 cm and fail after. Failure occurs mainly from the cracking of silicon nitride that is used as encapsulation layer of the substrate and as gate insulator. Also, it occurred by cracking of the microcrystalline silicon that is used as an active layer. This can be avoided by reducing the thickness of the active layer to 50 nm.
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Sabri Janfaoui. Electronique CMOS en silicium microcristallin sur substrat flexible transparent. Micro et nanotechnologies/Microélectronique. Université de Rennes1, 2012. Français. ⟨tel-02441266⟩

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