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標題: | 砷化銦鎵鰭式高載子遷移率電晶體之製作與傳輸特性及閘極控制機制之研究 Fabrication and Investigation of the Transport Properties and Gate Control Mechanism of Nanoscale InGaAs-based Fin-shaped High Electron Mobility Transistors |
作者: | Cheng-Jia Dai 戴承家 |
指導教授: | 吳肇欣(Chao-Hsin Wu) |
關鍵字: | 臨界電壓,高電子遷移率電晶體,增強型,等效電子遷移率,散射效應,空乏區, Threshold voltage,High-electron-mobility transistor,enhancement mode,effective mobility,scattering effect,depletion region, |
出版年 : | 2017 |
學位: | 碩士 |
摘要: | 在本論文中,我們提出一個可以解決三五族電晶體負臨界電壓問題的方法。傳統上可以藉由改變緩衝層厚度、改變電子供應層的位置或濃度、使用硫化氨((NH4)2S)進行表面鈍化以及使用「Pt sinking」技術使得高電子遷移率電晶體(High-electron-mobility transistor)之臨界電壓往正值移動。根據上述,已經有很多團隊藉由不同技術得到高效能常關型(normally-off)高電子遷移率電晶體。在本論文中,我們團隊也成功地在不使得效能衰退的情況下得到常關型(增強型)高電子遷移率電晶體。
首先我們介紹如何使用電子束負光阻ma-N 2403開發出奈米等級顯影圖形,並且成功製作出高深寬比(Aspect ratio, AR)之顯影圖形,其中最小線寬達到42奈米,我們也在乾蝕刻過後得到良好的圖形轉移(Pattern transfer)結果。 接著我們藉由一個四步驟的半導體製程製作出擁有良好開啟及次臨界特性的鰭式砷化銦鎵高電子遷移率電晶體。我們也探討了此電晶體在不同鰭寬度(Fin width)之下之傳輸特性,實驗結果顯示在此元件中庫倫散射(Coulomb scattering)是主要限制等效電子遷移率(Mobility)之機制。 我們也比較了鎳/金以及鈦/鉑/金兩種不同閘極金屬對元件電特性之影響。鎳/金為閘極之元件擁有較好的開啟以及次臨界特性,但是閘極漏電流是將來製作常關型元件中相當關鍵的問題。 再者,我們使用原子層沉積技術(Atomic layer deposition, ALD)結合原本的製程製作出鰭式金氧半高電子遷移率電晶體(Fin-MOSHEMT)以期可以克服閘極漏電流問題。但是由於閘極至通道距離過長以及半導體表面仍然不夠理想使得Fin-MOSHEMT的電特性仍然未比原本的FinHEMT好。 最後,我們分析了閘極側壁對於通道的控制機制,此控制機制是我們能夠成功得到增強型元件且不使得元件電特性衰退的主因。主因為:元件的通到會先被閘極側壁完全空乏(fully-depleted)早於被上方閘級關閉,因此,我們可以僅僅改變鰭寬度得到有良好開啟特性以及次臨界特性的電晶體。 In the thesis, we propose a new approach to overcome the negative threshold voltage issue for III-V transistors. Traditionally, threshold voltage can be modulated toward +VG direction by changing the thickness of barrier, changing the position or concentration of delta-doping layer, passivating the surface material of gate region by ammonium sulfide (NH4)2S or utilizing Pt-sinking technology for High-electron-mobility transistors. Lots of successful results were carried out to achieve high-performance enhancement-mode (normally-off) transistors so far. In this thesis we successfully fabricated E-mode transistors without performance degradation. First we introduce the development of negative photoresist ma-N 2403 which has the ability to creative nanoscale pattern. We successfully scaled down the high-aspect-ratio fin width to about 42 nm. The results also show excellent pattern transfer capability after dry etch. Then we carried out the fabrication by a 4-step process. InGaAs FinHEMTs were fabricated with high on-state and subthreshold performance. Moreover, we investigated the transport properties of InGaAs FinHEMTs with different fin width. The experimental results show that Coulomb scattering is dominant limiting term for effective mobility. We also compared the devices whose gate stack are Ni/Au and Ti/Pt/Au respectively. Ni/Au-gated devices show better on-state and subthreshold performance but the gate leakage issue becomes a critical issue for E-mode devices. Furthermore, we incorporated ALD-deposited Al2O3 to fabricate InGaAs Fin-MOSHEMT. The performance is much worse than FinHEMT’s because the distance between gate and channel is too large and the quality of surface is poor. Last, we analyze the mechanism of sidewall control of gate which can achieve E-mode transistors without any performance degradation. The channel is fully depleted by depletion regions from sidewall of gate much earlier than top gate does. Hence, E-mode transistors can be simply achieved by varying the size of fin width with excellent on-state and subthreshold performance. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/77903 |
DOI: | 10.6342/NTU201703012 |
全文授權: | 有償授權 |
顯示於系所單位: | 電子工程學研究所 |
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