在聚萘二酸乙二醇酯軟性基板上製備全透明銦鎵鋅氧化物薄膜電晶體元件之研究

Abstract

本研究在鍍有氧化銦錫（Indium Tin Oxide，ITO）導電薄膜之聚萘二酸乙二醇酯（Polyethylene Naphthalate，PEN）軟性基板上製備全透明銦鎵鋅氧化物（Indium-Gallium-Zinc Oxide，IGZO）薄膜電晶體（Thin-film Transistor，TFT）元件，同時也在玻璃基板上製備相同的TFT元件以供比較。本實驗共可分為兩部分，第一部分為固定閘極介電層總厚度，藉由調變介電層中SiOx/SiNy之厚度比（200 nm/0 nm、180 nm/20 nm、165 nm/35 nmm及150 nm/50 nm）以探討最佳之TFT元件特性，實驗結果顯示，以Al金屬為上電極、ITO-PEN為基板、SiOx/SiNy之厚度比例約為5：1（165 nm/35 nm）之TFT元件具有最佳之電性質，在汲極電壓（Drain Voltage，Vd）為5 V時，其臨界電壓（Threshold Voltage，Vth） = 1.5 V、次臨界擺幅（Sunsthreshold Swing，SS） = 0.99 V/decade、電流開關比（Ion/Ioff或On/Off Ratio）= 105、飽和載子遷移率（Saturation Carrier Mobility，sat） = 0.69 cm2/Vsec。第二部分沿用第一部分所得之最佳介電層結構，將Al上電極更換為氧化銦鋅（Indium Zinc Oxide，IZO）導電薄膜，以製成全透明TFT元件並探討不同上電極對元件特性之影響。以IZO導電薄膜為上電極之全透明TFT元件於可見光範圍之穿透度可達約80%，在Vd = 5 V時，Vth = 1 V、SS = 1.35 V/decade、On/Off Ratio = 104、sat = 0.44 cm2/Vsec。

This work presents the preparation and characterizations of fully transparent amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistor (TFT) on flexible polyethylene naphthalate (PEN) substrate coated with indium tin oxide (ITO) conducting layer. In TFT samples, the gate dielectrics were the double-layer SiOx/SiNy with various thickness ratios (200 nm/0 nm, 180 nm/20 nm, 165 nm/35 nmm and 150 nm/50 nm) deposited by plasma-enhanced chemical vapor deposition (PECVD) at temperature below 150C whereas the source/drain electrodes were aluminum (Al) or indium zinc oxide (IZO). The TFT samples containing Al as the electrodes and SiOx/SiNy gate dielectric with thickness ratio of 165 nm/35 nm exhibited the saturation field-effect mobility (sat) of 0.69 cm2/Vsec, threshold voltage (Vth) of 1.5 V, subthreshold swing (SS) of 0.99 V/decade and on/off current ratio (Ion/Ioff or on/off ratio) about 105 at an operating voltage (Vd) of 5 V. As to the fully transparent TFT sample containing IZO electrodes and the same gate dielectric structure, sat of 0.44 cm2/Vsec, Vth of 1 V, SS of 1.35 V/decade, and on/off ratio about 104 were achieved. UV-visible spectroscopy measurement indicated that the average transmittance of such a TFT is about 80% in visible-light wavelength range.