| Summary: | 碩士 === 明志科技大學 === 機械工程系機械與機電工程碩士班 === 105 === The purpose of this study was to develop a microelectromechanical sys-tem–compatible process (e.g., etching, lithography, sputtering) for a polyimide (PI) substrate. A thin-film transistor (TFT) array on a flexible PI substrate was demonstrated by fully etching aluminum (Al), indium gallium zinc oxide (IGZO), and aluminum oxide (Al2O3) on the substrate. In addition, we com-pared the TFT device dimensions of PI and glass.
We designed and examined two TFT structures with top-gate architecture. The proposed design concept of IGZO TFTs involved a channel width of 200 μm and lengths of 230, 190, 150, 100, 80, and 50 μm. In addition, the gap from gate to source or drain was 1–3 μm for the small-sized structures made on the plastic substrate.
A PI thin film (50 μm) was fixed onto a glass substrate with glue for a strong contact effect during exposure. Moreover, during the sputtering process, the surface roughnesses of IGZO, Al2O3, and Al on the PI substrate were well controlled to as low as 0.457, 0.326, and 12.3 nm, respectively, and their thicknesses were well controlled to as 520, 50, and 550 nm, respectively.
The optimized post annealing temperature of the IGZO thin film was ap-proximately 500 °C, as measured with a sheet resistance value of approxi-mately 0.8 kΩ/□. Adding hydrogen and argon decreased the sheet resistance to approximately 0.7 kΩ/□. However, the IGZO thin film enabled almost 100% transmission at 570–750 nm. Al2O3 with >90% transmission at 350–800 nm is key to the development of transparent conductive multilayer thin films.
The TFT devices in this study could be arbitrarily curled on the PI sub-strate. Therefore, the results are expected to facilitate the development of flexible electronic applications with high bending characteristics.
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