臺灣博碩士論文加值系統

自從奈米碳管於1998年被首次製作成奈米碳管電晶體之後，許多相關的研究便如火如荼的進行著。而許多奈米碳管電晶體的相關性質如雙極性電流特性等等也一一被發現。截至今日為止，蕭基位障模型是最普遍被人們所接受用來解釋奈米碳管電晶體之雙極性電流特性之模型。然而，卻只有一些直接證據可以證明奈米碳管電晶體是蕭基位障的元件。
在本論文中，我們提出了一種具有副閘極結構的元件結構，並且利用ISE TCAD元件模擬程式來模擬在不同副閘極電壓下的蕭基位障元件之電流特性。從模擬的結果中，我們發現因為蕭基位障會受到閘極電壓壓縮或是增厚，蕭基位障元件之ID-VG電流特性會出現雙極性的電流特性。而ID-VD特性則會因為汲極端的蕭基位障在不同的閘極電壓下，會受到汲極電壓的增加而降低位障高度，或是簡少位障厚度始得電流的變化出現完全不同的趨勢。
而當我們在副閘極施加正電壓時，也可以壓抑導帶的蕭基位障，並且增厚價帶的蕭基位障，因而使得電子的導通電流增加，並且減少電洞的導通電流，反之亦然。
實際的電性量測中發現蕭基位障薄膜電晶體與奈米碳管電晶體都可以量測到與模擬結果有相同趨勢的電流特性，而副閘極也可以影響其電流特性。然而奈米碳管電晶體因為其細微的準一維結構，使得其電流特性受到負閘極電壓的影響比起薄膜電晶體要小的多。
最後，我們將溫度模型引入模擬程式中來探討溫度對於蕭基位障薄膜電晶體與奈米碳管電晶體之作用。實際的量測結果中發現奈米碳管電晶體在不同溫度下的電流特性與模擬結果相符，但是蕭基位障薄膜電晶體會受到通道中的晶界所影響而出現與模擬結果相當大的差距。總而言之，本論文提出了數個直接證據說明奈米碳管電晶體可以視為一個單晶通道的蕭基位障元件。

Since the carbon nanotube field-effect transistor (CNTFETs) were proposed in 1998, lots of researches have been performed and many interesting properties have been reported, for example ambipolar behavior. Until now, Schottky barrier model (SB model) is the most accepted model to explain the ambipoar I-V behavior of CNTFETs. However, there are still little direct evidences to prove that the CNTFETs are Schottky barrier devices.
In this work, we proposed a novel device structure with source/drain sub-gates and used ISE TCAD simulation program to reveal the behavior of the Schottky barrier devices with various sub-gate biases. From the simulation results, we found that due to the thickness of Schottky barrier would be thickened or be suppressed by the gate bias, the ID-VG behavior of SB devices shows ambipolar characteristic. Besides that, as a result of that the Schottky barrier at drain side is lowered or thinned at different gate bias, the ID-VD behavior shows completely different trend as the drain voltage increases.
When we apply positive voltage at sub-gates, the Schottky barrier at conduction band will be suppressed and that at valance band will be thickened. Therefore, the electron current will increase and the hole current will decreases and vice versa.
Electrical measurement shows that the CNTFETs and TFTs exhibit the same I-V characteristics trend with the simulation results and that the sub-gates could affect the characteristics of both CNTFETs and SBTFTs. However, due to the tiny one-dimensional geometry of CNT, the sub-gates have much less effect on CNTFETs.
Finally, we included temperature model into the simulation program to investigate the temperature effect of SBTFTs and CNTFETs. The measured temperature effect of CNTFETs shows quite good agreement with the simulation results. However, as a result of grain boundary in actual SBTFTs channel, the measured results are quite different from the simulattion results.
Conclusively, this work provides several direct evidences to support that the CNTFETs could be treated as SB devices with single crystalline channel.

目錄
論文摘要（中文）.......................... i
論文摘要（英文）.......................... iii
誌謝...................................... v
目錄...................................... vi
圖目錄.................................... ix

第一章 緒論
1-1 奈米碳管的發現與製作方式..................................1
1-2 奈米碳管的結構與特性......................................2
1-3 奈米碳管在電子元件上的應用 ...............................3
1-4 奈米碳管與金屬接觸面之蕭基位障............................6
1-5 蕭基位障之調變............................................6
1-6 論文結構..................................................7

第二章 元件結構與製程步驟
2-1 緒論.....................................................16
2-2 元件模擬結構與所使用之模型...............................17
2-3 實作樣品之元件結構.......................................17
2-4 元件佈局.................................................18
2-5 元件製程步驟.............................................19
2-6 元件量測.................................................22

第三章 常溫電性模擬結果討論
3-1 緒論 ....................................................29
3-2 電極功函數對薄膜電晶體ID-VG特性之影響 ....................29
3-3 電極功函數對薄膜電晶體ID-VD特性之影響 ....................30
3-4 副閘極電壓對薄膜電晶體ID-VG特性之影響 ....................31
3-5 副閘極電壓對薄膜電晶體ID-VD特性之影響 ....................32
3-6 源極端副閘極電壓對基板電壓調變電流之影響 ................32
3-7 小結 ....................................................33

第四章常溫元件量測結果與討論
4-1 緒論.....................................................44
4-2 副閘極結構對電性與製程之影響.............................44
4-3 金屬電極材料對薄膜電晶體與奈米碳管電晶體ID-VG特性之影響 ..45
4-4 金屬電極材料對薄膜電晶體與奈米碳管電晶體ID-VD特性之影響 ..47
4-5 副閘極電壓對薄膜電晶體與奈米碳管電晶體ID-VG特性之影響 ....48
4-6 副閘極電壓對薄膜電晶體與奈米碳管電晶體ID-VD特性之影響 ....49
4-7 源極端副閘極電壓對基板電壓調變電流之影響.................50
4-8 小結 ....................................................50

第五章 低溫電性模擬結果與討論
5-1 緒論.....................................................69
5-2 溫度對薄膜電晶體ID-VG特性之影響 ..........................70
5-3 溫度對薄膜電晶體ID-VD特性之影響 ..........................71
5-4 副閘極電壓對薄膜電晶體在不同溫度下之ID-VG特性之影響 ......71
5-5 副閘極電壓對於薄膜電晶體在不同溫度下之ID-VD特性之影響 ....72
5-6 小結 ....................................................73

第六章 低溫電性量測結果與討論
6-1 緒論.....................................................80
6-2溫度對薄膜電晶體與奈米碳管電晶體ID-VG特性之影響 ...........80
6-3溫度對薄膜電晶體與奈米碳管電晶體ID-VD特性之影響 ...........82
6-4小結 .....................................................82

第七章結論與展望
7-1 結論.....................................................87
7-2 未來展望.................................................88

參考文獻 ..................................................90

參考文獻

[1]. S. Iijima, “Helical microtubules of graphitic carbon”, Nature, Vol. 354, pp. 56-58,1991
[2]. M. R. Falvo, G.J. Clary, R. M. Tayler II, V. Chi, F. P. Brooks Jr, S. Washburn and R. Superfine,” Bending and bucking of carbon nanotubes under large strain”, Nature, Vol.389, pp. 582-584, 1997
[3]. E. W. Wong,P. E. Sheehan, C. M. Lieber, ”Nanobeam mechanics: elasticity, strength and toughness of nanorods and nanotubes”, Science, vol.227, pp.1971-1975, 1997
[4]. Savas Berber, Young-Kyun Kwon, and David Tomanek, “Unusually High Thermal Conductivity of Carbon Nanotubes”, Phys. Rev. Lett., vol. 84, pp. 4613, 2000.
[5]. H. Dai, E. W. Wong, and C. M. Lieber, “Probing electrical transport in nanomaterials: conductivity of individual carbon nanotubes”, Science, vol. 272, pp.523-526, 1996.
[6]. S. Frank, p. Poncharal, Z. L. Wang, and W. A. deHeer, “Carbon nanotube quantum resistors”, Science, vol. 280, pp. 1744-1746, 1998.
[7]. R. Martel, T. Schmidt, H. R. Shea, T. Hertel, and Ph. Avouris, “Single- and multi-wall carbon nanotube field effect transistors”, Appl. Phy. Lett., vol. 73, pp. 2447-2449, 1998.
[8]. S. J. Tans, A. R. M. Verschueren, C. Dekker, “Room-temperature transistor based on a single carbon nanotube”, Nature, vol. 393, pp. 49-52, 1998.
[9]. T. W. Ebbesen, P. M. Ajayan, “Large-scale synthesis of carbon nanotubes”, Nature, vol. 358, pp. 220-222, 1992
[10]. Andreas Thess, et al.,“Crystalline Ropes of Metallic Carbon Nanotubes”. Science, vol. 273, pp. 483-487, 1996.
[11]. H. T. Soh, et al.,“Integrated nanotube circuits: Controlled growth and ohmic contacting of single-walled carbon nanotubes”, Appl. Phy. Lett., vol 75, pp. 627-629, 1999.
[12]. Teri Wang Odom, et al.,“Atomic structure and electronic properties of single-walled carbon nanotubes”, Nature, vol. 391, pp. 62-64, 1998.
[13]. W. Hoenlein, et al., ” Carbon nanotubes for microelectronics: status and future prospects”, Materials Science and Engineering C,Vol. 23,pp.663–669, 2003
[14]. M. S. Dresselhaus,et al., “Group theoretical concepts for carbon nanotubes”, Molecular Materials, vol. 4, pp. 27-40, 1994.
[15]. B. Q. Wei, R. Vajtai, and P. M. Ajayan, “Reliability and current carrying capacity of carbon nanotubes”, Appl. Phys. Lett., vol. 79, pp. 1172-1174, 2001.
[16]. F. Kreupl, A. P. Graham,et al., “Carbon nanotubes in interconnect applications”, Microelectronics Engineering, vol. 64, pp. 399-408, 2002.
[17]. Georg S. Duesberg, et al.,“Growth of Isolated Carbon Nanotubes with Lithographically Defined Diameter and Location”, Nano Letters., vol. 3 No. 2, pp.257-259, 2003
[18]. A. Bachtold,“ Aharonov-Bohm oscillations in carbon nanotubes”, Nature, vol. 397, pp. 673-675, 1999.
[19]. S. S. Wong, et al., “Carbon Nanotube Tips: High-Resolution Probes for Imaging Biological Systems”, J. Am. Chem. Soc. 120, 603-604, 1998.
[20]. A. G. Rinzler, et al., “Unraveling Nanotubes: Field Emission form an Atomic Wire”, Science, vol. 269, pp. 1550-1553, 1995.
[21]. J. Kong, et al., “Synthesis of Single Single-walled Carbon Nanotubes on Patterned Silicon Wafers”, Nature, vol. 395, pp. 878-881, 1998.
[22]. Wolfgang Hoenlein, “New Prospects for Microelectronics: Carbon Nanotubes”, Jpn. J. Appl. Phys. Vol. 41 (2002) pp. 4370–4374 Part 1, No. 6B, June 2002.
[23]. L. A. W. Robinson,et al., “Fabrication of self-aligned side gates to carbon nanotubes”, NANOTECHNOLOGY 14, pp. 290-293, 2003
[24]. S. J. Wind, et al., “Vertical scaling of carbon nanotube field effect transistors using top gate electrodes”, Appl. Phys. Lett., vol. 80 no. 20, 2002.
[25]. Sami Rosenblatt, et al.,“High performance electrolyte gated carbon nanotube transistors”, Nano Letters, vol. 2 No. 8, 869-872, 2002.
[26]. Fumiyuki NIHEY, Hiroo HONGO, Masako YUDASAKA, and Sumio IIJIMA, ” A Top-Gate Carbon-Nanotube Field-Effect Transistor with a Titanium-Dioxide Insulator”,Jpn. J. Appl. Phys., Vol. 41, pp. 1049–1051,Part 2, No. 10A, 2002
[27]. Ali Javey,et al.,” Carbon Nanotube Field-Effect Transistors with Integrated Ohmic Contacts and High-K Gate Dielectrics”, Nano Letters, vol. 4 No. 3, pp. 447-450, 2004.
[28]. J. Kong, et al.,“Nanotube molecular wires as chemical sensors”, Science, vol. 287, pp. 622-625, 2000.
[29]. V. Derycky, et al.,“Carbon nanotube inter- and intramolecular logic gates”, Nano Letters, vol. 1 No. 9, pp. 453-456, 2001.
[30]. Jie Han, “Carbon nanotube field-effect transistors”, Appl. Phys. Lett., Vol. 79 No. 20, 2001
[31]. M. Radosavljevic, J. Appenzeller, and Ph. Avouris, “High performance of potassium n-doped carbon nanotube field-effect transistors”, Appl. Phys. Lett., Vol. 84 No. 18, 2004
[32]. Cheng Lu, et al.,“Polymer electrolyte-gated carbon nanotube field-effect transistor”, Nano Letters, Vol. 4 No. 4, 2004
[33]. R. Martel, et al., “Ambipolar electrical transport in semiconducting single-wall carbon nanotubes”, Phys. Rev. Lett., Vol. 87 No. 25, 2001.
[34]. J. Appenzeller, et al., “Field-modulated carrier transport in carbon nanotube transistors”, Phys. Rev. Lett., Vol. 89 No. 12, 2002.
[35]. R. Martel,et al., “Carbon nanotube field-effect transistors and logic circuits”, PHYSICA B-CONDENSED MATTER ,Vol. 323,pp. 6-14, 2002
[36]. Xiaodong Cui, et al., “Controlling energy-level alignments at carbon nanotube/Au contacts”, NANO LETTERS, Vol.3 No. 6, 2003.
[37]. Jia Chen, et al.,“Self-aligned carbon nanotube transistors with novel chemical doping”, IEDM, 2004.
[38]. Yu-Ming Lin, Joerg Appenzeller, and Phaedon Avouris, “Novel carbon nanotubes FET design with tunable polarity”, IEDM, 2004.
[39]. C. Y. Chang and S. M. Sze, “Carrier Transport across Metal-Semiconductor Barriers”, Solid State Eclectron., 13, 1970
[40]. J. Bardeen and W. Shokley, “Deformation Potentials and Mobilities in Nonpolar Crystals”, Phys. Rev., 80,1950
[41]. S.M. Sze, Physics of Semiconductor Devices, 2nd ed., New York,Wiley, 1981.
[42]. T. I. Kamins, “Hall mobility in chemically deposited polycrystalline silicon.” J. Appl. Phys. 42, 4357-4365, 1971.
[43]. Mark S. Rodder,et. al., “On the temperature dependence of resistivity of polycrystalline silicon films”, Mat. Res. Soc. Symp. Proc., vol. 106, 1988.