ASSESSMENT OF FLEXIBLE SINGLE CRYSTAL SILICON THIN FILM TRANSISTORS

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Fen Bilimleri Enstitüsü, Türkiye

Tezin Onay Tarihi: 2019

Tezin Dili: İngilizce

Öğrenci: MUAMMER KOZAN

Asıl Danışman (Eş Danışmanlı Tezler İçin): Ahmet Oral

Eş Danışman: Selçuk Yerci

Özet:

Mechanically flexible large-area electronics are becoming more popular with such devices as sensors and medical devices. Organic, inorganic and organic/inorganic hybrid materials have been used for these systems. Although inorganic silicon is used for these systems, it is mostly in the amorphous or polycrystal form. Electron and hole mobilities for these forms are lower than single-crystal silicon. Therefore, to make a high-performance transistors single crystal silicon should be used. In this thesis, flexible single-crystal silicon thin-film transistors are tried to build and characteristics of the devices are examined. In the building process firstly, Si wafers are doped with SOD material and SOG is used as the dielectric material. To form the flexible single-crystal Si layer SOI wafers and KOH etched Si wafers are used. When silicon is thinned it is harder to handle; therefore, kapton tape is used as a plastic substrate. After forming the thin Si layer MOSFETs are designed to build in three different sizes. Gate lengths of these transistors are designed to be 50 μm, 75 μm, and 100 μm. Width of the transistors are tried to be kept the same around 400nm, thus different W/L ratios for each transistor can be achieved. By following these design parameters successful thick Si substrate MOSFETs are formed. Characterization for the built devices are done with Nanomagnetic Instruments ezHEMS device and Keithley 2612 source vi meter. With the help of the generally accepted transistor equations found IDS and mobility values are used to calculate some other transistor parameters. On the other hand, due to the fragile structure of thinned Si wafer, a successful flexible single-crystal thin film transistor cannot be built. However, it is shown that with a specifically designed cleanroom tools for thin silicon layer handling functional flexible thin-film transistors can be achieved.