氮化鎵材料擁有高電子飽和速度、低導通電阻以及高臨界電場。因此近年來，研發具有可用於無線通訊系統之高功率密度的射頻(Radio frequency, RF)元件，相當受到重視。矽基板氮化鎵元件由於氮化鎵材料的卓越特性及矽基板優良的散熱能力，對於發展高效率的高功率射頻元件而言相當具有潛力。到目前為止，用來製作矽基板氮化鎵高頻元件的基板皆為高阻值(> kΩ·cm)。然而，高阻值矽基板的強度較弱，容易導致磊晶後晶圓翹曲龜裂，除了無法成長較厚的氮化鎵緩衝層(>2 μm)之外，更限制了大面積的磊晶與量產能力，影響其能夠被廣泛應用的潛力。除此之外，高阻值的矽基板價格也較昂貴，不符合經濟效益。這使得低阻值矽基板的氮化鎵高頻元件相當具有研究價值，在低阻值矽基板上成長高絕緣性的氮化鎵緩衝層類似絕緣層在矽之上(SOI)的結構，可大幅降低低阻值矽基板的寄生效應，提升元件的高頻特性。而目前國內外對此方面的探討與研究相當缺乏，因此，本論文將磊晶與製作具有高絕緣性氮化鎵緩衝層的氮化鋁鎵/氮化鎵高電子遷移率電晶體。除了歐姆接觸的最佳化之外，我們採用T型閘極結構的高頻元件，可有效提升元件的本質轉導與高頻特性。
本論文研究主要以低阻值矽基板之GaN/AlGaN HEMTs之高頻元件製作與分析為主，藉由改變水平佈局並使用電子束微影微縮源極與汲極的間距，並且使用T型閘極 (T-gate)結構的高頻特性表現，同時提高元件在高頻(、)元件特性，基板阻值為60 Ω·cm可達48 GHz，可達100 GHz以上；基板阻值為2.5 mΩ·cm可達41 GHz，可達70 GHz最後藉由高頻等效電路模型對元件進行分析，根據等效模型的建立與模擬的結果，方便我們取得改善內部的參數，來調整佈局結構，並進一步提升元件特性。

Gallium Nitride (GaN)-based materials have high electron mobility, low on-resistance, and high critical electric field. Therefore, GaN has been used widely for high frequency (RF) and high power devices in recent years for various applications The GaN-on-silicon substrate devices have great potential for developing high-efficiency high-power RF devices due to their superior material properties of GaN materials and excellent heat dissipation of silicon substrates. Also, the cost is considerably lower than the typically used SiC substrate. So far, the substrates used to fabricate the high frequency GaN devices are mainly high-resistivity (> kΩ·cm) silicon substrates. However, the high-resistivity silicon substrates have a weak substrate strength so that the wafer will crack easily after the epitaxy process. As a result, it is difficult to grow thick (> 2 μm) buffer layer and limits the ability for large area epitaxy and massive production. Besides, the high-resistivity silicon substrates have relatively high cost compared to low-resistivity silicon substrate. In this work, we focus on using the high-insulation buffer layer on the low-resistivity silicon substrate to improve the high-frequency characteristics. We use low-resistivity silicon substrate to fabricate AlGaN/GaN HEMTs to investigate the effect on RF characteristics. The T-shaped gate is used to reduce gate resistance and improve intrinsic transconductance of the devices.
In this work, we focus on the design and analysis of GaN on low-resistivity silicon substrates devices. The E-beam lithography is used to fabricate the T-shape gate. The measured results demonstrate that the fT and fmax are up to 27 GHz and 71 GHz respectively for the 2.5 mΩ∙mm substrate and those are up to 44 GHz and 110 GHz respectively for the 60 Ω∙mm substrate.

目錄
誌謝 i
Abstract ii
摘要 iii
目錄 iv
圖表目錄 vii
表格目錄 x
第一章 簡介 1
1.1 研究動機 1
1.2 論文架構 1
第二章 氮化鎵材料與異質接面場效電晶體 3
2.1 材料特性之比較 3
2.1.1 寬能隙半導體 3
2.1.2 電子遷移率及飽和速度 4
2.1.3 高阻值矽基板與低阻值矽基板比較 5
2.2 AlGaN/GaN異質介面場效電晶體 8
2.2.1 自發性極化與壓電效應 8
2.2.2 Interlayer及緩衝層 12
2.2.3 歐姆接觸最佳化 15
2.2.4 元件結構及操作原理 16
2.3 高頻AlGaN/GaN異質介面場效電晶體 18
2.3.1 短通道效應(Short channel effect) 19
2.4 本章總結 22
第三章 元件設計與製程步驟 23
3.1 黃光微影製程(PhotoLithography) 23
3.2 元件隔離平台(Mesa isolation) 25
3.3 歐姆接觸(Ohmic contact) 26
3.3.1表面處理 27
3.3.2金屬層蒸鍍 28
3.3.3高溫熱退火處理(Rapid Thermal Annealing) 29
3.3.4 Transfer Length Method(TLM) 30
3.4 蕭特基閘極製作(Schottky gate) 31
3.4.1 T型閘極 32
3.5 鈍化層製作(Passivation) 35
3.6 接線窗口蝕刻(Via etching) 36
3.7 襯墊金屬(Pad metal) 37
3.8 源極區間電阻(Source Resistance)量測 37
3.9 本章總結 38
第四章 元件模型分析 39
4.1 高頻S參數量測 39
4.2 外部參數萃取及去嵌入(De-embedding) 40
4.2.1開路及短路測試元件萃取法 40
4.2.2 Cold-FET量測元件萃取法 42
4.3 高頻元件小訊號等效模型建立及分析 46
4.4 本章總結 47
第五章 量測結果與比較 48
5.1元件尺寸參數 48
5.2 直流量測結果 50
5.2.1 0.1μm 基板阻值2.5mΩ•cm元件量測結果與分析 50
5.2.2 0.1μm 基板阻值60Ω•cm元件量測結果與分析 54
5.3 不同基板阻值比較與高頻量測結果 60
5.3.1 元件等效模型分析 65
5.4 本章總結 67
第六章 總結 68
6.1 總結(Conclusion) 68
6.2 未來工作(Future work) 69
References 70

[1] Semiconductor TODAY Compounds&Advanced Silicon, vol. 9 , no. 4 , May 2014.
[2] Ambacher, “Growth and applications of group III-nitrides,” J. Physics D (Applied Physics), vol. 31, pp. 2653-2710, 1998.
[3] Likun Shen , “Advanced Polarization-Based Design of AlGaN/GaN HEMTs,” PhD thesis, University of California, Santa Barbara, 2004.
[4] B. Gelmont, K. Kim, and M. Shur, “Monte Carlo Simulation of Electron Transport in Gallium Nitride,” J. Appl. Phys., 74 (3), pp. 1818-1821, 1993.
[5] A. Dadgar, S. Fritze, O. Schulz, J. Hennig, J. Blasing, H. Witte, A. Diez, U. Heinle, M. Kunze, I. Daumiller, K. Haberland, A. Krost, “Anisotropic bow and plastic deformation of GaN on silicon,” J. Cryst. Growth, vol. 370, pp. 278281, May 2013.
[6] O. Ambacher, J. Smart, J. R. Shealy, N. G. Weimann, K. Chu, M. Murphy, W. J. Schaff, L. F. Eastman, R. Dimitrov, L. Wittmer, M. Stutzmann, W. Rieger, J. Hilsenbeck, "Two-dimensional electron gases induced by spontaneous and piezoelectric polarization charges in N-and Ga-face AlGaN/GaN heterostructures." Journal of Applied Physics , vol.85, pp. 3222-3233, May 1999.
[7] Fabio Sacconi, Aldo Di Carlo, P. Lugli, Hadis Morkoc, "Spontaneous and piezoelectric polarization effects on the output characteristics of AlGaN/GaN heterojunction modulation doped FETs."  IEEE Transactions Electron Devices, pp. 450-457, March 2001.
[8] Morkoç, Hadis, Roberto Cingolani, and Bernard Gil. "Polarization effects in nitride semiconductor device structures and performance of modulation doped field effect transistors." Solid-State Electronics, vol.43, pp. 1909-1927, 1999 .
[9] Junshuai Xue, Yue Hao, Jincheng Zhang, Jinyu NI, "Effect of high temperature AlN interlayer on the performance of AlGaN/GaN properties." IEEE Electron Devices and Solid-State Circuits, pp. 416-418, 2009.
[10] Lunchun Guo, Xiaoliang Wang, Cuimei Wang, Hongling Xiao, Junxue Ran, Weijun Luo, Xiaoyan Wang, Baozhu Wang, Cebao Fang, Guoxin Hu, "The influence of 1nm AlN interlayer on properties of the Al 0.3 Ga 0.7 N/AlN/GaN HEMT structure." Microelectronics Journal, vol.39, pp. 777-781, January 2008.
[11] Y. Dora, A. Chakraborty, S. Heikman, L. McCarthy, S. Keller, S. P. DenBaars, and U. K. Mishra, “Effect of ohmic contacts on buffer leakage of GaN transistors,” IEEE Electron Device Lett., vol. 27, no. 7, pp. 529531, Jul. 2006.
[12] Y.-W. Lian, Y.-S. Lin, J.-M. Yang, C.-H. Cheng, and S. S. H. Hsu, “AlGaN/GaN Schottky barrier diodes on silicon substrates with selective Si diffusion for low onset voltage and high reverse blocking,” IEEE Electron Device Lett., vol. 34, no. 8, pp. 981983, Aug. 2013.
[13] F. Sacconi, A. D. Carlo, P. Lugli, and H. Morkoc,” Spontaneous and piezoelectric polarization effects on the output characteristics of AlGaN/GaN heterojunction modulation doped FETs,” IEEE Trans. Electron Devices, vol. 48, no. 3, pp. 450457, Mar. 2001.
[14] S. R. Lee, D. D. Koleske, K. C. Cross, J. A. Floro, and K. E. Waldrip Sandia, “In situ measurements of the critical thickness for strain relaxation in AlGaN/GaN heterostructures,” Appl. Phys. Lett, vol. 85, pp. 6164-6166, 2004.
[15] G. H. Jessen, R. C. Fitch, J. K. Gillespie, G. Via, A. Crespo,D. Langley, D. J. Denninghoff, M. Trejo, and E. R. Heller, “Short-channel effect limitations on high-frequency operation of AlGaN/GaN HEMTs for T-gate devices,” IEEE Trans. Electron Devices, vol. 54, no. 10, pp. 2589–2597, Oct. 2007.
[16] Gregg H. Jessen, Robert C. Fitch, James K. Gillespie, Glen Via, Antonio Crespo, Derrick Langley, Daniel J. Denninghoff, Manuel Trejo, Eric R. Heller, "Short-channel effect limitations on high-frequency operation of AlGaN/GaN HEMTs for T-gate devices." IEEE Transactions Electron Devices, vol. 54, pp. 2589-2597, 2007.
[17] B. Jacobs, M. C. J. C. M. Kramer, E. J. Geluk, F. Karouta, "Optimisation of the Ti/Al/Ni/Au ohmic contact on AlGaN/GaN FET structures." Journal of Crystal Growth, vol.241, pp. 15-18, 2002.
[18] R. Vetury, N. Q. Zhang, S. Keller, U. K. Mishra, "The impact of surface states on the DC and RF characteristics of AlGaN/GaN HFETs." IEEE Transactions Electron Devices, vol. 48, pp. 560-566, March 2001.
[19] R. Kudrawiec, B. Paszkiewicz, M. Motyka, J. Misiewicz, J. Derluyn, A.Lorenz, K. Cheng, J. Das, and M. Germain, “Contactless electroreflectance evidence for reduction in the surface potential barrier in AlGaN/GaN heterostructures passivated by SiN layer,” Journal of Applied Physics , vol.104, no.9, pp.096108,096108-3, Nov 2008.
[20] T. Palacios, S. Rajan, A. Chakraborty, S. Heikman, S. Keller, S. P.DenBaars, and U. K. Mishra, “Influence of the dynamic access resistance in the gm and fT linearity of AlGaN/GaN HEMTs,” IEEE Trans. Electron Devices, vol. 52, no. 10, pp. 2117–2123, Oct. 2005.
[21] F. Qian, J. H. Leach, and H. Morkoc, “Small signal equivalent circuit modeling for AlGaN/GaN HFET： Hybrid extraction method for determining circuit elements of AlGaN/GaN HFET,” Proc. IEEE, vol. 98, no. 7, pp. 1140–1150, Jul. 2010.
[22] N. Moll, M. R. Hueschen, and A. Fisher-Colbrie, “Pulsed-doped AlGaAs/InGaAs pseudomorphic MODFET’s,” IEEE Trans. EZectron Devices, vol.35, no.7, pp.879,886, Jul 1988.
[23] P. J. Tasker and B. Hughes, “Importance of source and drain resistance to the maximum f of millimeter-wave MODFET's,” IEEE Electron Device Lett., vol. 10, pp. 291–293, July 1989.
[24] A. Koudymov, N. Pala, V. Tokranov, S. Oktyabrsky, M. Gaevski, R. Jain,J. Yang, X. Hu, M. Shur, R. Gaska, and G. Simin, “HfO2–III-Nitride RF switch with capacitively coupled contacts,” IEEE Electron Device Lett.,vol. 30, no. 5, pp. 478–480, May 2009.
[25] Y. R. Wu, M. Singh and J. Singh, ‘‘Device scaling physics and channel velocities in AIGaN/GaN HFETs: velocities and effective gate length,’’ IEEE Trans. Electron Devices 53, 588 (2006).
[26] R. Wang, G. Li, O. Laboutin, Y. Cao, W. Johnson, G. Snider,P. Fay, D. Jena, and H. Xing, “210-GHz InAlN/GaN HEMTs with dielectric-free passivation,” IEEE Electron Device Lett., vol. 32, no. 7, pp. 892–894, Jul. 2011.
[27] J. W. Chung, O. I. Saadat, J. M. Tirado, X. Gao, S. Guo, and T. Palacios,“Gate-recessed InAlN/GaN HEMTs on SiC substrate with Al2O3 passivation,” IEEE Electron Device Lett., vol. 30, no. 9, pp. 904–906, Sep. 2009.
[28] D. M. Geum, S. H. Shin, M. S. Kim, J. H. Jang, “75 nm T-shaped gate for In0.17Al0.83N/GaN HEMTs with minimal short-channel effect,” Electronics Letters , vol.49, no.24, pp.1536,1537, November 21 2013.
[29] H. F. Sun, A. R. Alt, H. Benedickter, C. R. Bolognesi, E. Feltin, J. F. Carlin, M. Gonschorek, N. Grandjean, and C. R. Bolognesi, “100 nm Gate (Al, In)N/GaN HEMTs Grown on SiC With fT=144 GHz,” IEEE Electron Device Lett., vol. 31, no. 4, pp. 293–295, Apr. 2010.