高載子飄移速率、高穩定度高分子與氧化鋅薄膜電晶體之介面與表面型態工程

Abstract

此研究提出開發可撓曲且大氣穩定、適合大面積生產之薄膜電晶體。研究的重點包含兩種材料：第一，溶液製程之3-己基噻吩；第二，原子層氣相沉積之氧化鋅。在3-己基噻吩研究中，專注於開發低溫溶液塗布製程來製作符合一般電性需求之薄膜電晶體。此外，更利用溶液塗布之封裝技術來增進3-己基噻吩薄膜電晶體之大氣穩定度。於原子層氣相沉積氧化鋅之研究中，則利用原子層氣相沉積技術開發高載子飄移速率且低起始電壓之可撓式薄膜電晶體。此外，還利用原子層氣相沉積之氧化鋁來鈍化氧化鋅薄膜電晶體，並大幅提升氧化鋅薄膜電晶體之閘極偏壓應力穩定性。 本研究的貢獻有四點：第一，提出並歸納空氣與封裝層對3-己基噻吩薄膜電晶體所造成之劣化，並成功的利用溶液塗布封裝技術來封裝元件。被封裝之3-己基噻吩薄膜電晶體於封裝過程中無明顯劣化，經5500小時儲存於大氣中後仍保持其原有電性。第二，開發出飽和溶液蒸汽壓的後處理，促使3-己基噻吩薄膜再流動，並使薄膜電晶體之載子飄移速率比未處理前增加84倍。第三，歸納介電層表面性質對原子層氣相沉積氧化鋅薄膜電晶體電性之影響。經由最佳化表面性質，在聚對苯二甲酸乙二醇酯(PET)塑膠基板上製備出高效能之薄膜電晶體，其載子飄移速率高出先前文獻達七倍。第四，利用原子層氣相沉積之氧化鋁來鈍化氧化鋅薄膜電晶體，並增加元件閘極偏壓應力穩定性。本研究結果可提供務實且有用的資訊，以促進適合大面積製程、可撓曲之薄膜電晶體相關產業發展。

In this study, we have demonstrated methods for fabricating air-stable flexible thin film transistor (TFT) that are suitable for large-area production, with two main focuses: (1) solution-processed poly (3-hexylthiophene) (P3HT) TFTs, and (2) atomic-layer-deposited (ALD) zinc oxide (ZnO) TFTs. With P3HT TFTs, we developed a low-temperature and solution-based fabrication process that yields high device performance. Additionally, we developed solution-processed thin-film encapsulation methods to obtain air-stability from the P3HT TFTs. With ZnO TFTs, we developed ALD processes for the ZnO film, the dielectric layer, and the passivation layer, achieving high field-effect mobility, low operation voltage, mechanical flexibility, and stability under a bias stress. The accomplishments of this study include: (1) we systematically determined the causes and characteristics of the air- and encapsulation-induced degradations of P3HT OTFTs, and based on the obtained knowledge, we developed a solution-based encapsulation process that yielded air-stable P3HT OTFTs (nearly free of degradation for > 5500 h in air) without encapsulation- induced degradation; (2) we demonstrated a solvent-vapor-annealing technique which induces reflow of the P3HT film, resulting in drastically improved field-effect mobility (by a factor of 84, to 0.11 cm2/V s); (3) we systematically studied the ZnO/dielectric interface to determine the factors governing the device performance, obtaining exceptionally high field-effect mobility from ALD ZnO TFTs on polyethylene terephthalate (PET) substrate, 16.9 cm2/V s, which was unprecedented for ALD ZnO-based TFTs; moreover, the TFTs exhibited excellent flexibility: nearly free of degradation upon repeated bending (1000 times) to 0.83 cm of radius; (4) we demonstrated ALD passivation of the ZnO TFTs, improving the bias-stress stability of the devices. The results from my research will provide practical information to the development of large-area-processible flexible TFTs.