奈米碳管網絡薄膜電晶體與奈米碳管網絡導電膜之研究

Abstract

自從 1991 年Iijima 發現奈米碳管(carbon nanotubes, CNTs)結構之後，由於其具有相當優異的電、 熱、機械、化學性質，吸引了廣泛的注意。單一單壁奈米碳管製作的碳管場效應電晶體應用在電子 工業是一長遠的目標，短期或中期比較可能的應用是利用大量單壁奈米碳管的平均效應來降低元件 間的變異，亦即碳管網絡薄膜電晶體。碳管網絡薄膜電晶體雖然已經有數年的歷史，但是性能尚不 理想。滲濾理論已經證實可以描述碳管網絡的導電能力，善用滲濾理論，搭配適當的製程條件以及 元件結構，有機會得到性能良好的碳管網絡薄膜電晶體。同樣善用滲濾理論，也可以得到導電率良 好的導電薄膜。因此本兩年期計畫預計以高性能的碳管網絡薄膜電晶體與導電膜為研究對象。 第一年度將先以滲濾理論計算碳管長度、密度、元件閘極長度、寬度對臨界長度的關係，據以決 定碳管塗佈的條件，以及元件長度、寬度的設計範圍，然後實際製作元件驗證。本計畫將以旋轉塗佈 方式製作碳管網絡，以符合低溫製程的需求。元件分為兩類，一為碳管網絡薄膜電晶體(CNT NWTFT)，一為碳管網絡導電膜(CNT NWCF)。元件實作將以矽晶片為基板，元件結構以區域性背閘 極結構為主，以簡化製程限制。第二年度計畫重點是將第一年度開發之低溫碳管網絡薄膜電晶體和碳 管網絡導電膜成果應用於透明可撓式基板，實現奈米碳管透明薄膜電晶體。此外，也深入分析碳管網 絡導電膜的可靠度。 本計畫如順利執行，可以建立高良率、開關電流比之碳管網絡透明薄膜電晶體，具軟性電子產業 應用價值。亦可建立碳管網絡導電膜技術，可製作超薄導電薄膜，在特定用途上取代金屬薄膜。在過 程中所研究的課題，包括滲濾理論、載子傳導機制、低溫製程、可撓式基板製程、低溫測試技術、微 區物性/化性分析等等，都具有學術及產業價值。

Since Iijima observed carbon nanotube (CNT) in 1991, CNT has attracted much attention because of its excellent electrical, thermal, mechanical, and chemical properties. The application of discrete single-walled CNT field effect transistor (SWNT FET) is a long term target. In medium and short term, using large amount of CNTs to minimize the device deviation, i.e., the CNT network thin-film transistor (CNT NWTFT) is more feasible. Although the CNT NWTFTs have been studied for several years, the characteristics are not good enough. It is known that the conductivity of the CNT NW can be modeled by the Percolation Theory. Using the percolation theory to design process conditions and device geometry may obtain high performance CNT NWTFTs. Similarly, using the percolation theory may also achieve high conductivity CNT network conduction films (CNT NWCFs). Therefore, we will focus on the CNT NWTFTs and CNT NWCFs. In the first year of this project, the percolation theory will be used to analysis the correlaton between the threshold length and the CNT length, the CNT density, the gate length, and the channel width. Real CNT NWTFTs will be designed and verified according to the analysis. In this project, the CNT NW will be formed by sequential spin-coating method to fulfill the requirement of low temperature process. Both CNT NWTFTs and CNT NWCFs will be fabricated on Si substrate in this year. Local bottom gate structure will be employed. In the second year, the low temperature CNT NWTFTs and CNT NWCFs will be fabricated on transparent flexible substrate to realize the total transparent CNT NW TFTs. The electromigration of the CNT NWCFs will be evaluated as well. In this project, we will setup the high yield, high on/off current ratio, and transparent CNT NW TFTs technology. This technology can be applied to the flexible electronics. This project will also setup the high yield and high conductivity CNT NWCFs technology for possibly replacing metal films at some special circumstances. The topics included in this project, the percolation theory, carrier transport, low temperature process, flexible substrate process, low temperature measurement, and micro area physical/chemical analysis, have both academic and practical values.