摘要
單壁奈米碳管具有良好抵抗電致遷移的能力以及高熱穩定性、高電流密度和高載子遷移率等特性，如此優異的材料性質，若作為電晶體的導電層，勢必能有效提升元件特性。將這類型碳管定向排列，不但能有效定位製程元件，往大面積積體化發展，亦能有效降低碳管間的接觸阻抗，增加載子在通道中傳輸能力。
在許多合成奈米碳管的方法中，化學氣相沉積法(CVD)是廣泛被業界使用作為鍍膜的製程方法，因此也是較能與現有半導體、光電製程相容的成長模式；但近年來奈米碳管在場效電晶體、發光二極體、非揮發式記憶體、感測器、可撓式透明基板的應用漸受到重視，因此可水平且平行排列成長的技術為研發重點。在奈米碳管元件應用特性上，平行成長碳管能有效降低碳管之間接觸電阻，較不易影響載子在碳管中的傳輸，能有效增加電晶體中的飽和電流。而利用單晶石英基板的特性能引導奈米碳管在基板上沿著某一特定方向成長，達到水平排列式結構；其中石英基板的不導電特性更可以有效減少元件在高頻訊號上的散失。若將此技術應用於元件中導電層的製作，在其上方再製作成三極結構，此上閘極結構的奈米碳管電晶體有較高開電流值、互導值，因為上閘極結構的關係，能避免碳管上吸附極性分子，磁滯大小視窗表現會較小，此技術運用於電晶體有顯著的發展。
本研究主旨為是發展以熱裂解化學氣相沉積法於石英基板上合成水平排列式奈米碳管陣列，並以碳管陣列上研製奈米碳管電晶體。單晶石英基板的特性在經過長時間高溫退火，表面會形成階梯狀的結構形貌來引導碳管平行排列成長於基板上，成長奈米碳管所使用的催化劑是鎳(Ni)/二氧化矽(SiO2)之雙層催化劑結構，其二氧化矽的結構使碳管能側向成長於基板上。在ST-cut規格的石英基板，則設計一實驗找出碳管成長排列方向與基板切面呈現九十度的角度關係，將有利於在基板上定位定向製作元件。成長奈米碳管之製程氣體為甲烷及氫氣之混合氣體，適當增加氫氣在混合氣體的比例，發現碳管因為氫氣帶走多餘的非結晶碳，有利於碳管的成長。從實驗中發現，透過不同的成長溫度會影響奈米碳管的密度與品質；不同的成長時間會影響奈米碳管的覆蓋性、準直性與品質。檢測奈米碳管石墨化的程度所使用的儀器是拉曼光譜(Raman spectrum)分析儀；量測碳管的直徑範圍及碳管之管徑分佈則利用原子力顯微鏡(AFM)。所成長的碳管長度能超過10 µm，密度最密能接近1 count/µm，IG/ID ratio能大於10以上，顯示碳管石墨化程度相當高。改變上層催化劑SiO2的鍍率則能有效控制奈米碳管的直徑分佈，當SiO2鍍率為1.0 Å/s，碳管平均直徑為1.413 nm；鍍率為0.5 Å/s，碳管平均直徑為1.283 nm；鍍率為0.2 Å/s，碳管平均直徑為0.944 nm。在研製元件及設計上，選用成長溫度900˚C、成長時間30分鐘的成長參數導入應用於電晶體結構的製作，因為這參數所成長之碳管有較佳的密度、長度，IG/ID ratio大於10以上，適合元件的發展。介電層部分，是利用atomic layer deposition (ALD) 技術製作高覆蓋性與高緻密度的Al2O3氧化層，閘極電流(漏電流)抑制在10-11A。在300組碳管水平陣列中，有9個電晶體的開電流能達到µA，開/關電流比約2-3；其中有1個電晶體，其次臨界曲線約為330 mV/decade，磁滯效應大小約為2 V左右，開/關電流比超過103的優異電性表現。

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