熱退火處理對於大氣電漿沉積銦鎵鋅氧化物薄膜電晶體之特性影響

Abstract

本論文利用大氣電漿沉積氧化銦鎵鋅作為元件的主動層，並且成功發展出高效能的薄膜電晶體。在Ｘ光繞射儀(XRD)分析中可以發現由大氣電漿沉積之氧化銦鎵鋅為非晶態。氧化銦鎵鋅薄膜對可見光的平均穿透率超過80%，並且具有3.78eV的能隙。這些特性使得大氣電漿沉積氧化銦鎵鋅具有應用於透明電路的潛力，以及能減少光漏電對元件的影響。我們利用矽晶片作為元件的基板並成長氧化矽當作絕緣層，隨後在沉積氧化銦鎵鋅薄膜後，對其在不同環境及不同溫度下進行退火處理，探討氧化銦鎵鋅薄膜在不同退火條件下對薄膜品質及元件特性的影響。我們在論文中使用X光繞射儀(XRD)、掃描式電子顯微鏡(SEM)、穿透式電子顯微鏡(TEM)、原子力顯微鏡(AFM)、X射線光電子能譜儀(XPS)，來分析及討論不同退火條件下氧化銦鎵鋅薄膜的表面形貌、缺陷密度、結晶型態等等，並且利用元件的I-V轉換曲線來進行元件特性探討。最後我們欲降低臨界電壓及次臨界擺幅而使用高介電係數材料取代氧化矽作為元件的絕緣層，氧化銦鎵鋅薄膜在最佳退火條件下及使用氧化鋁作為絕緣層後，發展出開關電流比1.04×108、電子遷移率8.6 cm2/V-s、臨界電壓0.75 V、次臨界擺幅0.28V/decade的高性能薄膜電晶體。

In this paper, we have successfully developed a high performance thin film transistor (TFT) with indium gallium zinc oxide (IGZO) active layer deposited by atmospheric pressure plasma jet (APPJ). IGZO films show amorphous phase in XRD analysis. IGZO films have over 80% transmittance of visible light and band gap energy 3.78eV. Therefore, IGZO films deposited by APPJ are suitable for transparent devices. Wide band gap can release the issue of photo-excited leakage current. We deposited IGZO thin films on silicon wafer which was covered with SiO2 and studied the effect of thermal annealing on IGZO films quality and properties of TFTs with IGZO as active layer. In this work, we discussed the IGZO films properties including surface morphology, roughness, structure and crystallinity by analysis equipments including SEM, AFM, XRD, TEM and XPS. We also used Agilent 4156C to analyze IGZO TFTs electrical characteristic. At the final, we substituted high-k material for SiO2 as gate dielectric for decreasing Vth and S.S. And the IGZO TFT with Al2O3 as gate dielectric shows excellent performance of μ = 8.6 cm2/V-s, Vth = 0.75 V, SS = 0.28V/dec, Ion/Ioff ratio of 1.04×108.