兆赫波(THz)元件需要比常用電極氧化銦錫(ITO)擁有更高穿透率之電極材料; poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)因其熱穩定性、穿透率以及可使用溶液配製，被廣泛應用在各種有機元件上。為了以PEDOT:PSS取代氧化銦錫使用在THz元件，我們利用微影製程以溶液製作PEDOT:PSS手指狀電極。
　　然而，傳統使用溶液準備之PEDOT:PSS在玻璃基板上的圖案製作無法獲得良好的均勻度。為改良此問題，我們修改了原本步驟，增加兩道氧電漿程序在原來的微影製程步驟: 一道用在旋塗之前，另一道在掀離之前，前者用來改善光阻圖案的潤濕性，後者能夠幫助去除阻礙掀離步驟之部分旋塗PEDOT:PSS。應用此兩道氧電漿程序，可製成乾淨且較均勻(從±33.9奈米到±10.6奈米)之PEDOT:PSS圖案。

Terahertz (THz) devices require electrode materials with higher transmittance than that of conventionally used indium–tin oxide (ITO); poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) is widely used for various organic devices owing to its high thermal stability, transmittance and solution-process capability. To replace ITO with PEDOT:PSS in our THz phase shifter, we fabricate finger-like patterned electrodes of PEDOT:PSS using the solution process of photolithography.
However, conventionally patterning PEDOT:PSS layers on glass substrates via the solution processes does not necessarily provides good uniformity. To improve this problem, we modify the conventional processes, introducing two additional oxygen (O2) plasma processes into the conventional photolithography processes: one is just before spin-coating PEDOT:PSS, and the other is before the lift-off process. The former improves the wettability on the patterned photoresist surface, and the latter would help partially remove the spin-coated PEDOT:PSS that impedes the lift-off process. Applying two additional processes, enables fabricating more uniform, defect-free PEDOT:PSS patterns; the deviation of thickness has been improved from ±33.9 nm to ±10.6 nm. We also discuss how the U-shape cross-sections of the patterns appear depending on the exposure conditions of O2 plasma.

Contents
摘要 .....1
Abstract ......2
Acknowledgements ....3
Contents ....4
List of Figures ....6
Chapter 1 Introduction ....10
1.1 Terahertz Technology ....10
1.2 LC-based THz phase shifters ....11
1.3 Transparent electrode ....11
1.4 Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) ....12
1.5 Patterning PEDOT:PSS ....13
1.6 Purpose of the study ....14
Chapter 2 Experiments and methods ....15
2.1 Equipment ....15
2.2 Materials ....17
2.3 Sample preparation ....18
2.3.1 Glass cleaning ....18
2.3.2 Photolithography ....19
Chapter 3 Results and discussions ....22
3.1 Preliminary study of PEDOT:PSS ....22
3.1.1 Glass cleaning ....22
3.1.2 Thickness of PEDOT:PSS film ....25
3.1.3 Conductivity of PEDOT:PSS film ....27
3.2 Patterning of photoresist ....28
3.2.1 Parameters in photolithography ....28
3.2.2 Patterned photoresist ....32
3.3 Patterning of PEDOT:PSS ....34
3.3.1 Unsucceeded patterning of PEDOT:PSS ....35
3.3.2 Surfactant of PEDOT:PSS ....36
3.3.3 Concentration of surfactant ....37
3.4 PEDOT:PSS pattern ....42
3.4.1 Profile of PEDOT:PSS pattern ....42
3.4.2 Disadvantages of PEDOT:PSS pattern ....44
3.5 Additional process for optimization ....46
3.5.1 Oxygen plasma treatment before spin-coating ....46
3.5.2 Oxygen plasma treatment before lift-off ....55
3.6 PEDOT:PSS pattern made by optimized procedure ....61
Chapter 4 Conclusion ....63
Chapter 5 References ....64

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