應用超臨界流體於氧化鋁閘極介電層有機薄膜電晶體之研究

Abstract

在此論文裡，我們研究了高介電常數材料與薄膜電晶體在超臨界二氧化碳流體混合水的熱處理下其電性的改變。首先，在室溫下，利用電子槍蒸鍍系統成長極薄的氧化鋁薄膜，厚度約為16奈米，為了取代傳統的高溫退火製程，我們使用了溫度約150°C超臨界流體混合水的技術，為了驗證超臨界流體混合水能有效的使水分子進入到氧化鋁，進而減少薄膜的缺陷密度，我們經由紅外線光譜儀、熱脫附常壓游離質譜儀與X射線光電子能譜來做材料分析，結果均顯示於氧化鋁薄膜內氧的含量增加，而厚度為16奈米氧化鉿薄膜在閘極電壓3伏特的操作下，其單位面積漏電流約為3.9×10-9 A/cm2，傳導機制亦由原本未經過處理的量子穿隧效應轉換為熱放射效應，以上主要的原因是由於氧化鋁薄膜的缺陷密度減少。 除此之外，我們利用電子槍蒸鍍系統，在低溫下製造氧化鋁閘極介電層有機薄膜電晶體，但不可避免地，氧化鋁薄膜在沉積過程中，由於懸鍵和晶格的錯位，會產生電性上的缺陷，這些缺陷會使閘極漏電流增加。而如何減少這些缺陷密度在氧化鋁閘極介電層有機薄膜電晶體的製造中是很重要的。因此，我們發現經由超臨界流體技術的處理之後，氧化鋁閘極介電層有機薄膜電晶體有較好的元件特性，其漏電流、臨界電壓、次臨界擺幅和場效移動率都有顯著的提升。這些改善主要是因為超臨界流體的技術，能有效修補懸鍵，進而減少薄膜的缺陷密度。在給予閘極定電壓與汲極定電流的元件特性劣化分析中，在超臨界超臨界二氧化碳流體混合水的熱處理下，氧化鋁閘極介電層有機薄膜電晶體擁有較佳的可靠度。由這些結果均顯示，藉由超臨界流體混合水的技術，能減少薄膜的缺陷密度。

In this study, supercritical fluids (SCF) technology is employed originally to effectively improve the properties of low-temperature-deposited metal oxide dielectric films. In this work, 16 nm ultra-thin Aluminum Oxide (Al2O3) films are fabricated by E-gun method at room temperature, and replacing the conventional high temperature annealing with supercritical fluids treatment at 150 °C. The supercritical fluids act a transporter to deliver H2O molecule into the Al2O3 films for repairing defect states. After this proposed process, the absorption peaks of Al-O-Al bonding apparently raise and the quantity of oxygen in Al2O3 film increases from FTIR and TDS measurement, individually. The leakage current density of 16 nm Al2O3 film is cut down to 3.9×10-9 A/cm2 at |Vg| = 3 V, and the conduction mechanism is transferred from quantum tunneling to thermal emission because of the significantly reducing the defects in the Al2O3 film. Supercritical fluids technology is also proposed to effectively passivate the defects in Al2O3 gate dielectric on organic thin film transistors (OTFTs) at low temperature (150 °C). After the treatment of supercritical fluids mixed with water and propyl-alcohol, the OTFT exhibited superior transfer characteristics and lower threshold voltage. The improvement in electrical characteristics can be verified due to the significant reduction of defects in Al2O3 gate dielectric on organic thin film transistors. Under bias stress and current stress, the device, which was treated with SCCO2 with co-solvent and HMDS, has smaller value of threshold voltage shift. Also, the mobility and sub-threshold swing of this device are unchanged. It indicated that this device had better reliability than others.