新穎式金屬閘極於非晶矽薄膜電晶體之特性研究

Abstract

近年來液晶顯示器面板的生產製造上，因日韓台三地多數大廠的投入發展，在製程技術上愈來愈成熟，生產成本來愈來愈低。其中Array製作的金屬閘極部分，多數大廠仍使用純鋁材料，利用濺鍍設備進行閘極金屬的成膜。但純鋁材料使用上易有因為後續高溫製程而有hillock的產生，再者鋁與Si和ITO間仍有金屬擴散問題。故先進大廠仍使用Mo、Ti或Cr等其他金屬夾在純鋁材料前後成膜。雖此類方法能有效解決上述的問題，卻無形中增加了材料成本和製作成本。為有效降低材料成本與生產稼動成本以提升製造廠的□爭力。現行先進面板製造廠改使用Al-Nd的鋁合金靶材進行閘極金屬的濺鍍成膜。使用一段時間，發現使用Al-Nd的鋁合金材料後，延伸出以下三項問題，一是出現在一般製程中，仍因後續溼式與乾式蝕刻製程影響，造成薄膜缺陷，而在高溫高溼的信賴性測試時，發生斷線亮點的問題。二則是Al-Nd與ITO接觸阻抗偏高，造成功率消耗等其他問題。三則是因Nd屬地球上稀有資源，無法大量使用且易造成日後材料成本提升等問題。為改善遇到的狀況，遂續尋找一新的金屬材料取代。很快得在材料廠的協助下，我們開發了Al-Ni-La的新鋁合金靶材。 故本篇論文即針對新開發出來的Al-Ni-La新鋁合金材料進行非晶矽薄膜電晶體中閘極金屬材料替換的相關驗證。首先針對薄膜特性部分，與原Al-Nd合金的材料特性作比較。並在不改變現行製程方式下，作元件的電性與信賴性比較。以有效降低面板製造廠的生產成本，提高產品良率。經相關實驗比較驗證後，確實可得此材料能有效改善現階段所遇到的多項問題，並於此篇論文發表後，已成功將此一新材料成功導入現行液晶顯示器面板製程廠中，讓新產品順利在市場上大量使用。

In the recently TFT-LCD fabrication demands, like Japan, Korea and Taiwan, some problems exist while developing AM-LCD. Thin film transistor (TFT) arrays are widely used in liquid crystal displays (LCDs) industry, in which high productivity and cost effectiveness .The thin films of Al alloys have many advantageous characteristics over those of pure Al . While hillocks are formed on thin films of pure Al. Thus, a high temperature processes such as chemical vapor deposition (CVD) of SiN and a-Si can be used even after the gate lines. And pure Al and Si or ITO have diffusion problem. The gate of TFT consists of multi-layers of pure Al and other metals such as Mo, Ti, and Cr of several 10nm in thickness. The roles of these metal layers are to achieve ohmic contacts with indium tin oxide (ITO) and a-Si, and also to be a barrier to prevent atomic inter-diffusions between pure Al with ITO or Si in the interconnection lines. This strategy is high cost and long throughput. It is widely recognized that aluminum (Al) alloys are very useful materials for gate electrode of amorphous-silicon (a-Si:H) thin film transistor (TFT) arrays in liquid crystal displays(LCDs). For instance, thin films of aluminum-neodymium (Al-Nd) alloys are widely used for the gate lines of TFT because of its stability at high temperature. But aluminum-neodymium (Al-Nd) alloys have three problem, one is have porous after deposition during wet or dry etching. The TFT is fail. Another is Al-Nd film have high contact resistance with ITO. The other is addition of the rare-earth metal has only minute impact on electrical resistivities of the alloy, unlike other alloying elements which tend to increase electrical resistivities. In this study, Al-Ni-La was applied to serve as gate electrodes in order to release this problem and simplified the TFT process steps. We check characteristic of Al-Ni-La film. Then we compare with the gate of Al-Nd film on TFT-LCD and Al-Ni-La. We got better than then. And the product with gate electrode of Al-Ni-La on TFT-LCD is in display market.