臺灣博碩士論文加值系統

此研究製作出魚鰭寬度(Fin width)分別為50nm、80nm、110nm 在藍寶石(Sapphire)基板上之氮化鋁鎵/氮化鎵(AlGaN/GaN)鰭式場效電晶體(FinFET)。透過直流電特性、脈衝電壓、高頻S參數分析比較元件參數。
當魚鰭寬度越小時，臨界電壓(Vth) 向正值靠近，符合理論值。同時此研究在魚鰭寬度越小時，輸出電流變小，連帶使得轉導值(gm)變小、次臨界值擺幅(S.S.)增大、電流截止頻率(fT)降低、最大增益頻率(fmax)降低，原因可能來自於過長的魚鰭長度，使源極電阻增加所致。
而魚鰭寬度減小時，單位表面積增加，連帶使得表面缺陷增加，可能因此形成漏電路徑，造成元件特性變差。
本實驗透過蒸鍍導電層，使電子束微影可以用在不導電基板材料，並透過光罩設計減少電子束微影的曝光時間及微影成本，使得不導電基板之奈米級研究變得更加可行。

Three types of AlGaN / GaN fin-shaped field effect transistors (FinFETs) on sapphire substrate, with fin widths (Wfin) of 50nm, 80nm, and 110nm, have been fabricated. Each device have been characterized by DC characteristics, pulse voltage, and high frequency S-parameters. The threshold voltages of each device shift toward positive value as the fin width decreases, which is correspond with the theoretical value. However, the narrorer fin width gives to smaller output power, which leads to smaller transconductance (gm), larger sub-threshold swing (S.S.), slower cutoff frequency (fT) and maximum gain frequency (fmax). The reason may be that the influence of source resistance (Rs), which enhances when fin length (Lfin) increases. When the fin width decreases, the unit surface area and surface defects increase, forming leakage paths, which causes the deterioration of the device characteristics. In this experiment, nano-scaled fin width of FinFETs on sapphire substrate was fabricate, it will be more feasible to develop nano-level research on non-conductive substrates.

摘要 i
ABSTRACT ii
致 謝 xii
目 錄 xiii
表目錄 xvi
圖目錄 xvii
第一章 緒論 1
1.1 前言 1
1.2 氮化鎵之HEMT背景與發展 2
1.3 研究動機 3
第二章 基礎理論、電晶體量測介紹 7
2.1氮化鎵材料特性簡介 7
2.2 氮化鋁鎵/氮化鎵 HEMT材料簡介 8
2.2.1自發極化 (Spontaneous Polarization , PSP) 9
2.2.2壓電極化 (Piezoelectric Polarization , PPE) 10
2.3 橫向型高電子遷移率場效電晶體工作原理 11
2.4傳輸線模型(Transmission Line Model , TLM) 13
2.5鰭式場效電晶體(FinFET) 15
2.5.1簡介 15
2.5.2 鰭式結構在HEMT基板上的模擬 16
2.6電子束微影(Electron Beam Lithography,EBL)技術簡介 20
2.6.1曝寫方式 21
2.6.2電子束光阻劑 (E-Beam Resist) 22
2.6.3曝寫參數影響 24
2.7電晶體量測系統 25
2.7.1霍爾量測(Hall measurement) 25
2.7.2 HEMT直流特性原理與量測 26
2.7.3電流崩塌(Current collapse)特性原理與量測 32
2.7.4 高頻S參數特性原理與量測 34
第三章 實驗方法與製程步驟 36
3.1微米級光罩設計 36
3.1.1 源極、閘極、汲極(Source、Gate、Drain)光罩設計 36
3.1.2 高台(MESA)光罩設計 37
3.1.3 高台側壁鈍化(MESA sidewall passivation)光罩設計 37
3.1.4接墊(Pad)光罩設計 38
3.1.5閘極絕緣層(Gate insulator)光罩設計 38
3.2 電子束微影圖案設計 40
3.2.1 電子束近接效應(Proximity effect) 40
3.2.2 正型阻劑製程 41
3.2.3 負型阻劑製程 44
3.3 元件基板 44
3.4 Fin HEMT元件製程步驟 45
3.4.Ⅰ 魚鰭通道(Fin channel)製程 46
3.4.Ⅱ 對準記號(Alignment mark)製程 50
3.4.Ⅲ 高台隔離(Mesa Isolation)製程 52
3.4.Ⅳ 高台側壁鈍化(Mesa sidewall passivation)製程 53
3.4.Ⅴ源汲極歐姆接觸 (Ohmic Contact)製程 54
3.4.Ⅵ閘極絕緣層(Gate insulator)製程 57
3.4.Ⅶ 閘極蕭基接觸(Shocky contact)製程 59
3.4.Ⅷ 接墊(Pad)製程 61
3.5 Fin HEMT元件完成圖 61
第四章 實驗結果與討論 64
4.1鰭式結構 64
4.1.1 正型光阻AFM結果 64
4.1.2 負型光阻SEM結果 65
4.2傳輸線模型 68
4.2.1 鈦/鋁在HEMT試片之歐姆接觸特性分析 68
4.3 元件直流電性分析 70
4.3.1 Id-Vd、Id –Vg輸出特性曲線 70
4.3.2 Ig –Vg輸出特性曲線 78
4.3.3 磁滯現象與開關比 81
4.3.4 崩潰電壓 81
4.3 元件電流崩塌(current collapse)分析 82
4.4 元件高頻(RF)分析 86
4.4.1 S參數分析 86
第五章 結論與未來工作 90
5.1 結論 90
5.2 未來工作 91
參考文獻 93

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