摘要
日益增长的信息技术对超高集成度、高速、低功耗集成电路的需求，驱使晶体管的尺寸越来越小，随之而来的问题是作为MOS栅氧化物和DRAM电容介质的SiO_2迅速减薄至物理极限。另一方面，新材料的应用推动薄膜晶体管(TFT)平板显示技术迅猛发展。由此，我们对纳米ZnMgO薄膜在MOS晶体管和透明TFT的应用进行了多方面的探索研究，取得如下创新性结果：
1) ZnMgO纳米薄膜的生长与材料结构采用物理蒸发低温沉积系统(PELD)在不同衬底上，包括玻璃，石英和硅，制备了不同晶相的ZnMgO薄膜。因为生长温度低，生长的ZnMgO／衬底界面清晰，没有明显的氧化物过渡层。在氧气气氛下，经过400～700℃退火的薄膜，XRD测试半峰宽均小于0.4°，说明薄膜晶体具有良好的结晶性和热稳定性。
2) Al／C-ZnMgO／Si MIS结构电学性能和热稳定性 制备立方相C-ZnMgO MIS结构研究其电学性能。在1MHz测试频率下，C-ZnMgO材料的介电常数为10.5；大于1MHz，介电常数随频率增加而逐渐明显降低。通过电容—电压(I-V)和电流—电压(C-V)特性测试，我们研究了不同退火温度对MIS结构性能的影响。经过550～900℃退火处理的C-ZnMgO MIS结构的漏电流密度降低了3个数量级。发现550℃退火的C-ZnMgO薄膜中可动离子缺陷密度最小，这是因为退火后薄膜中的杂质缺陷得到有效的复合。高温900℃退火的薄膜有最好的界面特性结果，界面处形成了硅酸盐化合物MgSi_xO_y，进而提高了界面质量。但是薄膜中杂质缺陷增加。这可能是因为在900℃下Zn离子与O离子从ZnMgO薄膜中析出并且向表面移动，从而增加了薄膜中的缺陷，与此同时，界面处有硅酸盐化合物MgSi_xO_y的形成从而提高了界面质量。这些材料结构与电学性能的研究有助于推动C-ZnMgO在MOSFET工艺中的应用。
The fast development of information technology requires integrated circuit to be greater integrated, faster functioned and lower power-consumed, which lead to continuous shrinkage of MOS and DRAM feature size and the thickness of MOS gate dielectrics (SiO_2) would soon scale down to its physical limit. Under this trend the high-K dielectrics is a promising solution for the future development of CMOS technology. Another trend is the new material systems application in TFT for next generation panel display technology. We have made a serics of investigation on fabrication and characteristics of high-K ZnMgO thin film on MOSFET and ZnMgO stacks on TFT. Main innovation results are listed as below:
Highly (002) oriented Cubic ZnMgO (C-ZnMgO) films were grown in a physical evaporation low-temperature deposition system (PELD). As-grown thin films show clear interface on the silicon. The thin films have good thermal stability and good crystal quality with smaller than 0.4° FWHM observed by XRD spectra after annealing at 400-700 ℃ in O_2 atmosphere. After fabrication into MIS structure, good dielectrics property with dielectrics constant 10.5 was attained. Permittivity is de-gradated when frequency more than 1MHz. C-ZnMgO thin film after 400℃ annealing was found to greatly reduce leakage current down to 3 orders. Of 550℃ annealing leads to high quality thin film. The reason is that at 550℃ annealing the mobile ions defect in the film were annihilated. Of 900℃ annealing shows reverse characteristics. The mobile ions defect in the film is noticeable which are attributed to Zn migrating toward surface and oxygen loss due to evaporation from the surface. But the film shows high quality interface characteristics, which could be attributed to the formation of Mg silicate layer in the interface. Those structural and electrical characteristics are helpful to MOSFET processing.
Great efforts have been made for the high-K C-ZnMgO MOSFET process. The current-voltage (I-V) characteristics of MOSFET were systematically studied. The output characteristic value is lower than our Medici tool simulation result and the output curve shows insufficient in the saturation region. Those are attributed to
引文
[1] 施敏(S.M.Sze)，现代半导体器件物理，北京，科学出版社，1981：63-65
[2] G.C. Dacey and I.M. Ross, Upinolar field-effect transistor, Proc, IRE 41, 1950: 970
[3] Augus I. Kingon, Jon-paul Maria, S. K. Streiffer, Alternative dielectrics to silicon dioxide for memory and logic devices, Nature 406, 2000: 1032-1038
[4] http://public.itrs.net
[5] Shin-ichi Takagi and Mariko Takayanagi, Experimental evidence of inversion-layer mobility lowering in ultrathin gate oxide metal-oxide-semiconductor field-effect-transistorswith direct tunneling current, Jpn. J. Appl. Phys. Part 1, 4B, 2002: 2348-2352
[6] D.A. Muller et al. The electronic structure at the atomic scale of ultra-thin gate oxides, Nature 399, 1999: 758-761
[7] S.P. Tang et al., Evaluating the minimum thickness of gate oxide on silicon using first-principles method, Appl. Surf. Sci. 135, 1998: 137-142
[8] J.B. Neaton et al., Electronic Properties of the Si/SiO_2 Interface from First Principles, Phys. Rev. Lett. 85, 2000: 1298-1300
[9] M. Alam et al., Proc Electronchem Soc., 2002-2: 365-367
[10] B.E. Weir et al. Gate oxides in 50 nm devices: thickness uniformity improves projected reliability, Tech. Dig. Int. Electron Devices Meet, 1999: 437-440
[11] M.Cao et al., Boron diffusion and penetration in ultrathin oxide with poly-Si gate, IEEE Trans. Electron Devices Lett. 19, 1998: 291-293
[12] J. M. Hergenrother et al., Evanescent-mode analysis of short-channel effects in fully depleted SOI and related MOSFETs, Tech. Dig. Int. Electron Devices Meeting, 1997: 75-76
[13] H.-S. Wong et al., Device scaling limits of Si MOSFET's and their application dependencies, Tech. Dig. Int. Electron Devices Meeting, 1997: 427-429
[14] G.lucovski et al, Er doped nanocrystalline ZnO planar waveguide structures for 1.55 μm amplifier applications, Appl. Phy. Lett. 74, 1999: 2005-2007
[15] G.D. Wilk, R. M. Wallace and J.M. Anthony, High-κ gate dielectrics: Current status and materials properties considerations, J. Appl. Phys. 89, 2001: 5243-5275
[16] D.S. Yu et al., Al_2O_3/Ge-On-Insulator n- and p-MOSFETs with Fully NiSi and NiGe Dual Gates, IEEE Elec. Dev. Lett. 25, 2004: 138-140
[17] P.D. Ye, et al., GaAs metal-oxide-semiconductor field-effect transistor with nanometerthin dielectric grown by atomic layer deposition, Appl. Phy. Lett. Vol. 83, 2003: 180-182
[18] Zhonghe Jin, Hoi S. Kwok and Man Wong., Germanium Thin Film Formation by Low-Pressure Chemical Vapor Deposition, IEEE Elec. Dev. Lett. 12, 1998: 502-505
[19] D.A. Buchnan et al., Effect of thickness on the physical properties of ITO thin films, Tech. Dig. Int. Electron Device Meet, 2000: 223-225
[20] L. Manchanda et al., Gate quality doped high K films for CMOS beyond 100 nm: 3-10 nm Al_2O_3 with low leakage and low interface states, IEEE Elec. Dev. Lett. 9, 1998: 502-504
[21] S. Guha et al., Atomic beam deposition of lanthanum- and yttrium-based oxide thin films for gate dielectrics, Appl. Phys. Lett. 77, 2000: 2710-2712
[22] J. Kwo et al., High ε gate dielectrics Gd_2O_3 and Y_2O_3 for silicon, Appl. Phys. Lett. 77, 2000: 130-132
[23] J.A. Gupta et al., Interfacial layer formation in Gd_2O_3 films deposited directly on Si (001),Appl. Surf. Sci. 173, 2001: 318-326
[24] H.J. Osten et al., High-k gate dielectrics with ultra-low leakage current based on praseodymium oxide, Tech. Dig. Int. Electron Device Meet, 2000: 653-656
[25] Kshem Prasad et al., Ce-doped TiO_2 Insulators in Thin Film Electroluminescent Devices, Jpn. J. Appl. Phys. 36, 1997: 5696-5702
[26] M. Gurvitch et al, Study of thermally oxidized yttrium films on silicon, Appl. Phys. Lett. 51, 1987: 919-921
[27] J.A. Gupta et al., Gadolinium silicate gate dielectric films with sub-1.5 nm equivalent oxide thickness, Appl. Phys. Lett. 78, 2001: 1718-1720
[28] J.J. Chambers et al., Yttrium silicate formation on silicon: Effect of silicon preoxidation and nitridation on interface reaction kinetics, Appl. Phys. Lett. 77, 2000: 2385-2387
[29] T.P. Ma, High-k gate dielectrics for scaled CMOS technology, 6th Int. Conf. Solid-state & IC Tech. Proc. Vol.1, 2001: 297-302
[30] Kaupo Kukli et al., Tailoring the dielectric properties of HfO_2-Ta_2O_5 nanolaminates, Appl. Phys. Lett. 68, 1996: 3737-3739
[31] Kaupo Kukli et al., Properties of Ta_2O_5-Based Dielectric Nanolaminates Deposited by Atomic Layer Epitaxy, J. Electronchem. Soc. 144, 1997: 300-306
[32] S.J. Wang et al., Electrical properties of crystalline YSZ films on silicon as alternative gate dielectrics, Semicond. Sci. Tech. 16, 2001: L13-L18
[33] T.M. Pan et al., Comparison of Ultrathin CoTiO_3 and NiTiO_3 High-k Gate Dielectrics, J. Appl. Phys. 89, 2001: 3447-3452
[34] P.K. Weimer, the TFT-a new thin-film transistor, Proceedings of the IRE, Vol.50, 1962: 1462-1469
[35] P.G. LeComber, Amorphous-silicon field-effect device and possible application, Electron Lett., 15, 1979: 179-181
[36] M. Matsumura and H hayama, Ultra-fast 0.5 μm CMOS Circuitsin Fully Depleted SOI Films, IEEE Tran. Electron, Devices, ED-27, 1980: 2194-2199
[37] A.J. Snell and W.E. Spear, The lifetime of injected covers in. amorphous silicon pn junctions, Appl. Phys. A26, 1981: 83-91
[38] Yi He, R. Hattori, and J. Kanicki, Improved a-Si: H TFT pixel electrode circuits for active-matrix organic light emitting displays, IEEE Tran Electron Devices, Vol. 48, No. 7, 2001: 1322-1325
[39] J.H. Kim, Yongtaek Hong and J. Kanicki, Amorphous silicon TFT-based active-matrix organic polymer LEDs, IEEE Electron Device Letters, vol. 24, no. 7, 2003: 451-453
[40] C. Yoo, D.J. Kim and K.L. Lee, Development and evaluation of a CMOS sensor-based digital intra-oral radiographic system, IEE Electronics Letters, vol. 41, no. 2, 2005: 65-66
[41] H. Hara, M. Sakurai, M. Miyasaka, S. W. B. Tam, S. Inoue and T. Shimoda, Solid-State Circuits Conference, 2004. ESSCIRC 2004. Proceeding of the 30th European, 2004: 403-406
[42] T. Tsukada, Scaling theory of liquid-crystal displays addressed by thin-film transistors, IEEE Trans. Electron Devices, Vol.45, No.2, 1998: 387-393
[43] M. Itoh et al., High-Resolution Low-Temperature Poly-Si TFT-LCDs Using a Novel Structure with TFT Capacitors, SID 96 Digest, 4.1, 17-20
[44] M. Ikeda et al., TFT-LCD Gate and Data Bus-Line Design and Process Technologies, SID 96 Digest, 4.1, 17-20, SID 95 Digest, 4.2, 11-14
[45] Y. Matsueda et al., High Performance Circuitry for Integrated Poly-Silicon Drivers, SID 98 Digest, 30.1, 879-882
[46] C.W. Tang and S.A. Vanslyke, Organic Electroluminescent Diodes, Appl. Phys. Lett. 51, 1987: 913-915
[47] Sang Chul Lim et al., New method of driving an OLED with an OTFT, Synthetic Metals 151, 2005: 197-201
[48] J.F. Sarver et al., Phase equilibriums and manganese-activated fluorescence in the system Zn_3(PO_4)_2-Mg_3(PO_4)_2, J. Electrochem. Soc. 106, 1959: 960-963
[49] A. Ohtomo et al., Mg_xZn_(1-x)O as a Ⅱ-Ⅵ widegap semiconductor alloy, Appl. Phys. Lett. 72, 1998: 2466-2468
[50] C. W. Tenget al., Refractive indices and absorption coefficients of Mg_xZn_(1-x)O alloys, Appl. Phys. Lett. 76, 2000: 979-981
[51] A. Ohtomo et al., Thermal stability of supersaturated Mg_xZn_(1-x)O. alloy films and Mg_xZn_(1-x)O/ZnO heterointerfaces, Appl. Phys. Lett. 75, 1999: 4088-4090
[52] A. Ohtomo et al., Structure and optical properties of ZnO/Mg_(0.2)Zn_(0.8)O superlattices, Appl. Phys. Lett. 75, 1999: 980-982
[53] T. Makino et al., Room-temperature luminescence of excitons in ZnO/(Mg, Zn)O multiple quantum wells on lattice-matched substrates, Appl. Phys. Lett. 77, 2002: 975-977
[54] H.D. Sun et al., Stimulated emission induced by exciton—exciton scattering in ZnO/ZnMgO multiquantum wells up to room temperature, Appl. Phys. Lett. 77, 2000: 4250-4252
[55] S. Choopun, R. D. Vispute, W. Yang, R.P. Sharma, and T. Venkatesan, H. Shen, Realization of band gap above 5.0 eV in metastable cubic-phase Mg_xZn_(1-x)O alloy films, Appl. Phys. Lett. 80, 2002: 1529-1531
[56] D.J. Qiu, H.Z. Wu, N.B. Chen, T.N. Xu, Characterizations of cubic ZnMgO films grown on Si(111) at low substrate temperature, Chin. Phys. Lett. 20, 2003: 582-584
[57] 贺洪波和范正修，功能材料，2000，31(增刊)，77-78
[58] H. Yamada et al., Improvement of crystallinity of ZnO thin film and electrical characteristics of film bulk acoustic wave resonator by using Pt buffer layer Vacuum 74, 2004: 689-692
[59] Y. K. won, Enhancement-mode thin-film field-effect transistor using phosphorus-doped (Zn, Mg)O channel, Appl. Phy. Lett. 84, 2004: 2685-2687
[60] Kenji Nomura, Thin film transistor fabricated in single-crystalline transparent oxide semiconductor, Science vol. 300, 2003: 1269-1272
[61] J.R. Arthur et al., Interaction of Ga and As_2 Molecular Beams with GaAs Surfaces, J. Appl. Phys. 39, 1968: 4032-4034
[62] K. Ogata, K. Sakurai, S.Z. Fujita, S.G. Fujita and K. Matsushige, Journal of Crystal Growth, vol. 214, 2000: 312
[63] Chen NB, Wu HZ and Qiu DJ, Structural and optical studies of Mg_xZn_(1-x)O films grown on sapphire, ACTA Physics Sinica, 53(1), Jan. 2004: 311-315
[64] Qiu DJ, Wu HZ, Chen NB and Tian WJ, Cubic Mg_xZn_(1-x)O films grown on Si(111), Journal of Inorganic Materials, 18(6), NOV 2003: 1385-1388
[65] Qiu DJ, Wu HZ, Xu XL and Chen NB, Comparisons of structural and optical properties of ZnO films grown on sapphire and Si(001), Chin. Phys. Letts. 19(11), Nov. 2002: 1714-1717
[66] X. Huang et al., Sub 50-nm FinFET: PMOS, Tech. Dig. Int. Electron Devices Meet. 1999: 67-70
[67] I.C. Kizilyalli, R.Y.S. Huang and P.K. Roy, MOS transistors with stacked SiO_2-Ta_2O_5-SiO_2 gate dielectrics for giga-scale integration of CMOS technologies, IEEE Electron Device Lett. 19, 1998: 423-425
[68] T.M. Klein et al., Evidence of aluminum silicate formation during chemical vapor deposition of amorphous Al_2O_3 thin films on Si (100), Appl. Phys. Lett. 75, 1999: 4001-4003
[69] E.P. Gusev et al. High-resolution depth profiling in ultrathin Al_2O_3 films on Si, Appl. Phys. Lett. 76, 2000: 176-178
[70] M. Balog, M. Schieber, S. Patai and M Michman, Thin films of metal oxides on silicon by chemical vapor deposition with organometallic compounds, J. Gryst. Growth 17, 1972: 298-301
[71] R.C. Smith et al., Low Temperature Chemical Vapor Deposition of ZrO_2 on Si(100) Using Anhydrous Zirconium (Ⅳ) Nitrate, J. Electrochem. Soc. 147, 2000: 3472-3476
[72] S.A Campbell et al., MOSFET transistors fabricated with high permitivity TiO_2 dielectrics, IEEE Trans. Electron Devices 44, 1997: 104-109
[73] X. Guo, X. Wang, Z. Luo, T.P. Ma and T. Tamagawa, High quality ultra-thin (1.5 nm) TiO_2-Si_3N_4 gate dielectric for deep sub-micron CMOS technology, Tech. Dig. Int. Electron Devices Meet 1999: 137-140
[74] X.B. Lu et al, Investigation of high-quality ultra-thin LaAlO_3 films as high-k gate dielectrics, J. Phys. D: Appl. Phys. 36, 2003: 3047-3050
[15] G.B. Wilk and R.M. Wallace, Electrical properties of hafnium silicate gate dielectrics deposited directly on silicon, Appl. Phys. Lett. 74. 1999: 2854-2856
[76] S.Chatterjee et al., Electrical properties of deposited ZrO_2 films on ZnO/n-Si substrates, Semicond. Sci. Technol. 18, 2003: 92-96
[77] Duenas S et al., The electrical-interface quality of as-grown atomic-layer- deposited disordered HfO_2 on p- and n-type silicon, Semicond. Sci. Technol. 19, 2004: 1141-1148
[78] Baohong Cheng et al., Advanced silicide for sub-0.18 μm CMOS on ultra-thin (35 μm) SOI, IEEE Trans. Electron Devices 46, 1999: 261-263
[79] Seiichi Miyazaki, characterization of high-k gate dielectric/silicon interface, Applied Surface Science 190, 2002: 66-72
[80] Wenjie Qi, Renee Nieh and Byoung Hun Lee, Electrical and reliability characteristics of ZrO_2 deposited directly on Si for gate dielectric application, Appl. Phys. Lett. 77, 2000: 3269-3271
[81] S.M. Sze, Physics of Semiconductor Devices, Wiley, New York, 1981: 277-289
[82] S. Wolf, Silicon Procession for the VLSI Era, vol.3-The Submicron MOSFET, Lattice Press, Sunset Beach, CA, 1995
[83] S.M. Sze, Physics of Semiconductor Devices, John Wiley & Sons, New York, 1981: 220-221
[84] E.H. Nicollian and J.R. Brews, Metal Oxide Semiconductor Physics and Technology, John Wiley & Sons, New York, 1982: 1-3
[85] Y.P. Tsividis, Operation and Modeling of the MOS Transistor, McGraw-Hill, New York, 1987
[86] ITRS roadmap 2004 update
[87] Stephen A. Campbell, The Science and Engineering of Microelectronic Fabrication-2nd Edition, Publishing House of Electronics Industry, BeiJing, 2003. 1: 426-427
[88] 荒井英铺，集成电路，翻译：绍春林等，北京：科学出版社，2000
[89] 甘学温，数字CMOS VLSI分析与设计基础，1992年2月第一版，北京：北京大学出版社，30-38
[90] 刘恩科，朱秉升，罗晋生等，半导体物理，1994年4月第四版，北京：国防工业出版社
[91] G.D. Wilk, R. M. Wallace and J.M. Anthony, High-κ gate dielectrics: Current status and materials properties considerations, J. Appl. Phys. 89, 2001: 5243-5275
[92] J.S. Suehle et al., Challenge of high-κ gate dielectrics for future MOS device, 2001 6th International Symposium on Plasma Process-induced Damage, May, Monterey, CA, USA., 14-15
[93] S. Arulkumaran et al., Improved de characteristics of AlGaN/GaN high-electron-mobility transistors on AlN/sapphire templates, Appl. Phys. Lett. 81, 2002: 1131-1133
[94] S. Harada et al., Improved channel mobility in normally-off 4H-SiC MOSFETs with buried channel structure, Mater. Sci. Forum 389-393, 2002: 1069-1072
[95] D.C. Look et al, As-doped p-type ZnO produced by an evaporation/sputtering process, Appl. Phys. Lett. 85, 2004: 5269-5271
[96] K.K. Kim et al, Realization of p-type ZnO thin films via phosphorus doping and thermal activation of the dopant, Appl. Phys. Lett. 83, 2003: 63-65
[97] Y.R. Ryu, T.S. Lee and H.W. White, Properties of arsenic-doped p-type ZnO grown by hybrid beam deposition, Appl. Phys. Lett. 83, 2003: 87-89
[98] K. Nomura et al., Thin-film transistor fabricated in single-crystalline transparent oxide semiconductor, Science 300, 2003: 1269-1272
[99] S. Masuda, Transparent thin film transistors using ZnO as an active channel layer and their electrical properties, J. Appl. Phys. 93, 2003: 1624-1630
[100] R.L. Hoffman, B.J. Norri, J.F. Wager, ZnO-based transparent thin-film transistors, Appl. Phys. Lett. 82, 2003: 733-735
[101] P.F. Carcia, R.S. McLean, M.H. Reilly and G. Nunes, Transparent ZnO thin-film transistor fabricated by rf magnetron sputtering, Appl. Phys. Lett. 82, 2003: 1117-1119
[102] J. Nishii et al., High mobility thin film transistors with transparent ZnO channels, Jpn. J. Appl. Phys., Parts2 42, 2003: L347-349
[103] Y. Ohya, T. Niwa, T. Ban and Y. Takahashi, Thin Film Transistor of ZnO Fabricated by Chemical Solution Deposition, Jpn J. Appl. Phys., Partsl 40, 2001: 297-298
[104] J. H. Kim, Yongtaek Hong and Kanicki, Amorphous silicon TFT-based active-matrix organic polymer LEDs, IEEE Electron Device Letters, Vol. 24, No. 7, 2003: 451-453
[105] Y. Kwonet et al., Enhancement-mode thin-film field-effect transistor using phosphorus-doped (Zn, Mg)O channel, Appl. Phys. Lett., vol. 84, 2004: 2685-2687
[106] Zhibin Xiong et al., Characteristics of high-K spacer offset-gated polysilicon TFTs, IEEE Transactions on Electron Devices, Vol. 51, No. 8, 2004: 1304-1308
[107] P.G. LeComber, Amorphous-silicon field-effect device and possible application Electron Lett. 15, 1979: 179-181
[108] 谢永瑞 编著，VLSI概论，清华大学出版社，Sept．2002
[109] Joon-Chul Goh et al., A new pixel circuit for active matrix organic light emitting diodes, IEEE Electronic Device Letters, Vol.23, No.9, 2002: 544-546
[110] R.L. Hoffman, ZnO-channel thin-film transistors: channel mobility, J. Appl. Phys. 95, 2004: 5813-5819
[111] Faruque M. Hossain et al., Modeling and simulation of polycrystalline ZnO thin-film transistors, J. Appl. Phys. 94, 2003: 7768-7777
[112] S. Choopun, R. D. Vispute, W. Yang, R.P. Sharma, and T. Venkatesan, H. Shen, Realization of band gap above 5.0 eV in metastable cubic-phase Mg_xZn_(1-x)O alloy films, Appl. Phys. Lett. 80, 2002: 1529-1531
[113] P. D. Ye et al., GaAs metal-oxide-semiconductor field-effect transistor with nanometerthin dielectric grown by atomic layer deposition, Appl. Phy. Lett. 83, 2003: 180-182
