臺灣博碩士論文加值系統

中文摘要
本實驗主要研究方向在探討銅金屬薄膜經高溫退火後凝聚的行為，並進一步改善凝聚現象的發生。在本實驗中，利用改變不同銅薄膜的厚度(50nm或200nm)、是否在Cu/TaN間添加10nm Ta中介層及不同的基材材料(Si或SiO2/Si)等參數，經不同溫度(400℃-900℃)30分鐘真空退火後，以四點探針(four point probe)量測片電阻值的變化，以θ-2θ X光繞射(θ-2θ X-ray diffraction)分析相的變化，利用掃瞄式電子顯微鏡(SEM)觀察試片表面形態，利用歐傑電子分析儀(AES)及拉塞福背向散射分析(RBS)做試片縱深成份分析，以X光射線光電子能譜儀(XPS)來分析薄膜表面的化學鍵結，並利用穿透性電子顯微鏡(TEM)觀察銅薄膜晶粒大小。
從實驗的結果可以知道，當銅薄膜厚度為200nm時，不論銅薄膜是直接沉積在TaN上，或是在Cu/TaN間加了一層Ta中介層，都不會有凝聚現象的發生。而銅凝聚的現象只發生在銅薄膜較薄(50nm)，且直接鍍製於TaN之上時；若在Cu/TaN間添加了一層10nm的Ta中介層，銅薄膜凝聚的現象明顯的改善。由RBS及XPS的分析結果中可以知道，在Cu/TaN間添加一層Ta中介層，經高溫退火之後(700℃)， Ta會擴散至銅薄膜的表面，形成一層cap-layer，阻礙銅的凝聚。比較未添加Ta中介層及在Cu/TaN間添加Ta中介層的SEM照片後也可以發現，添加一層Ta中介層可以明顯減緩銅晶粒的成長，進一步降低銅凝聚的情形。然而，從實驗中的結果也可以發現，在添加Ta中介層後會因為TaN中的N遭到稀釋，因此降低TaN高溫阻障效果。另外，實驗的結果也顯示出，銅薄膜凝聚與否與基材材料並沒有一直接的關係。但是，從實驗中的結果也可以發現，利用SiO2/Si為基材可以明顯阻止Cu-Si間的反應。
從本實驗的結果可以知道，增加銅薄膜的厚度以及在Cu/TaN間添加一層Ta中介層，可以明顯的阻止銅薄膜在TaN擴散阻障層上的凝聚行為。基材材料對銅凝聚的現象雖然沒有直接的關連性，然而，以SiO2/Si為基材可以明顯的阻止以Si為基材時，銅與矽之間的反應。

Abstract
In this work, the agglomeration behavior of copper thin film after high temperature annealing is investigated. Copper film thickness (50nm or 200nm), with or without a 10nm Ta interlayer between Cu and TaN, and different substrate materials (Si or SiO2/Si) were used as the experimental factors. After samples were annealed at various temperatures (400℃-900℃) in vacuum for 30 min, material characteristics were analyzed. The change of sheet resistance was measured by four-point probe. θ-2θ X-ray diffraction was used for phase identification, and scanning electron microscopy (SEM) was employed to investigate the surface morphology. Compositional depth profiles were measured by Auger electron spectroscopy (AES) and Rutherford backscattering spectrometry (RBS). X-ray photoelectron spectroscopy (XPS) was used to examine chemical bonding states, and transmission electron microscopy was employed to investigate copper grain size.
Experimental results reveal that either with or without a Ta interlayer between Cu and TaN, no copper agglomeration was observed when the copper has a thickness of 200nm. Copper agglomeration was only observed when copper has a thickness of 50nm. It was also observed that copper agglomeration was significantly improved while a Ta interlayer was added between Cu and TaN. When a Ta interlayer was added between Cu and TaN, RBS and XPS reveal that after high temperature annealing (700℃), Ta will diffuse to the copper surface and forming a cap-layer. The cap-layer might prevent copper agglomeration. By comparing the SEM photographs of samples with or without a Ta interlayer, it is observed that the grain growth of copper was slow down when a Ta interlayer was induced. The slow grain growth may result in the prevention of copper agglomeration. However, the interposed Ta layer would also dilute the overall nitrogen concentration in the barrier layer, and consequently brought the failure of the barrier. From the results of this experiment, the connection between copper agglomeration and substrate material was not obviously. Besides, the reaction between Cu and Si could be prevented when the SiO2/Si substrate was used.
From the results of this experiment, copper agglomeration on TaN diffusion barrier could be prevented significantly by increasing copper thickness and adding a Ta interlayer between Cu and TaN. The relationship between copper agglomeration and substrate material was not obvious. However, using SiO2/Si as substrate material could prevent reaction between Cu and Si.

目錄
第一章 前言與研究目的 1
1-1前言 1
1-2 研究目的 4
第二章 理論基礎 7
2-1 電阻-電容延遲(RC delay) 7
2-2 TaN擴散阻障層 9
2-3 銅金屬導線 11
2-4 薄膜凝聚現象探討 11
2-5 文獻中對薄膜凝聚現象的探討 18
第三章 實驗方法與步驟 19
3-1 實驗材料 19
3-2 實驗設備 20
3-2.1 濺鍍系統 20
3-3.2退火系統 20
3-3 實驗流程 23
3-4 鍍膜分析 28
3-4.1 片電阻值及厚度量測 28
3-4.2 結晶繞射分析 30
3-4.3 SEM表面觀察 32
3-4.4 AES成份、縱深分析 32
3-4.5 XPS化學態分析 34
3-4.6 拉賽福背向散射(RBS)分析 34
第四章 實驗結果與討論 36
4-1 銅/阻障層於矽晶片上之行為 36
4-1.1 片電阻量測 36
4-1.2 XRD及SEM分析 38
4-2 銅/阻障層於覆有二氧化矽之矽晶片上之行為 51
4-2.1 片電阻量測 51
4-2.2 XRD及SEM分析 53
4-3 實驗參數對界面反應及銅凝聚的影響 65
4-3.1 添加Ta中介層 65
4-3.2 銅薄膜厚度 68
4-3.3 Si基材與SiO2/Si基材的差異 69
第五章 結論 77
參考文獻 79

參考文獻
1.X. W. Lin, and D. Pramanli, “Future interconnect technologies and copper metallization”, Solid State Technology, 41(10), 63 (1998).
2.R. J. Gutmann, T. P. Chow, A. E. Kaloyeros, W. A. Lanford, and S. P. Murarka, “Thermal stability of on-chip copper interconnect structures”, Thin Solid Films, 262 (1-2), 177 (1995).
3.N. Awaya., H. Inokawa, E. Yamamoto, Y. Okazaki, M. Miyake, Y. Arita, and T. Kobayashi, “Evaluation of a copper metallization process and the electric characteristics of copper-interconnected quarter-micro CMOS”, IEEE Trans. Electron Devices, 43 (8), 1206 (1996).
4.J. Tao, N. W. Cheung and C. M. Hu, “Metal electromigration damage healing under bidirectional current stress”, IEEE Electron Device Letters, 14 (12), pp.554-556 (1993).
5.T. Nitta, T. Ohmi, T. Hoshi, S. Sakai, K. Sakaibara, S. Imai and T. Shibata, “Evaluating the Electromigration Resistance of Copper Interconnects Employing a Newly Developed Accelerated Life-Test Method”, J. Electrochem. Soc., 140 (4), 1131 (1993).
6.C. S. Liu, L. J. Chen, “Interfacial reactions of ultrahigh-vacuum-deposited Cu thin films on atomically cleaned (111)Si. I. Phase formation and interface structure”, J. Appl. Phys, 74 (8), 5001 (1993).
7.C. S. Liu, L. J. Chen, “Effects of substrate cleaning and film thickness on the epitaxial growth of ultrahigh vacuum deposited Cu thin films on (001)Si”, Appl. Surf. Sci., 92, 84 (1996).
8.S. W. Russell, S. A. Rafalski, R. L. Spreitzer, J. Li, M. Moinpour, F. Moghadam, and T. L. Alford, “Enhanced adhesion of copper to dielectrics via titanium and chromium additions and sacrificial reactions”, Thin Solid Films, 262 (1-2), 154 (1995).
9.K. W. Kwon, C. Ryu, R. Sinclair, and S. S. Wong, “Evidence of hrteroepitaxial growth of copper on beta-tantalum” Appl. Phys. Lett., 71 (21), 3069 (1977).
10.Q.-T. Jiang, F. Rick, Hieu “Robbie” Lam, and M. Jay, “Investigation of Ta , TaN and TaSiN barriers for copper interconnects”, IEEE International Interconnect Technology Conference 1999, pp. 125 –127, 1999.
11.T. Hara, K. Sakata, A. Kawaguchi, and S. Kamijima, “Control of agglomeration on copper seed layer employed in the copper interconnection”, Electrochemical and Solid-State Letters, 4 (11), C81 (2001).
12.R. Kröger, M. Eizenberg, E. Rabkin, D. Cong, and L. Chen, “The role of kinetics in the nucleation and void formation in copper films produced by chemical vapor deposition”, J. Appl. Phys, 88 (4), 1867 (2000)
13.T. Nogami, J. Romero, V. Dubin, D. Brown, E. Adem, “Characterization of the Cu/Barrier metal interface for copper interconnects”, IEEE International Interconnect Technology Conference 1998, pp.298 –300.
14.J.-T. No, J.-H. O, C. Lee, “Evaluation of Ti-Si-N as a diffusion barrier between copper and silicon”, Materials Chemistry and Physics, 63 (1), 44 (2000).
15.J. S. Chen and J. L. Wang, “Diffusion barrier properties of sputtered TiB2 between Cu and Si”, J. Electrochem. Soc., 147 (5), 1940 (2000).
16.S. J. Wang, H. Y. Tsai, S. C. Sun, and M. H. Shiao, “Thermal stability of sputtered tungsten carbide as diffusion barrier for copper metallization”, J. Electrochem. Soc., 148 (9), G500 (2001).
17.J.-Y. Lee and J.-W. Park, “Diffusion barrier property of Molybdenum nitride films for copper metallization”, Jpn, J. Appl. Phys., part1, 35 (8), 4280 (1996).
18.T. Oku, E. Kawakami, M. Uekubo, K. Takahiro, S. Yamaguchi, and M. Murakami, “Diffusion barter property of TaN between Si and Cu”, Applied Surface Science, 99 (4), 265 (1996).
19.M. T. Wang, Y. C. Lin, and M. C. Chen, “Barrier properties of very thin Ta and TaN layers against copper diffusion”, J. Electrochem. Soc., 145 (7), 2538 (1998).
20.M. H. Tsai, S. C. Sun, C. E. Tsai, S. H. Chuang, and H. T. Chiu, “Comparision of the diffusion barrier properties of chemical-vapoer-deposited TaN and sputtered TaN between Cu and Si”, J. Appl. Phys, 79 (9), 6932 (1996).
21.G. S. Chen, and S. C. Huang, “Intrinsic properties and barrier behaviors of thin films of sputter-deposited single-layered and alternately layered tantalum nitrides (Ta2N/TaN)”, J. Electrochem. Soc., 148 (8), G424 (2001).
22.Y. K. Lee, Khin Maung Latt, Kim Jaehyung, Kangsoo Lee, “Study of diffusion barrier properties of ionized metal plasma (IMP) deposited TaN between Cu and SiO2”, Materials Science in Semiconductor Processing, 3 (3), 179 (2000).
23.K. Holloway and P. M. Fryer, “Tantalum as diffusion barrier between copper and silicon”, Appl. Phys. Lett. 57 (17), 1736 (1990).
24.T. Laurila, K. Zeng, J. K. Kivilahti, J. Molarius and I. Suni, “Failure mechanism of Ta diffusion barrier between Cu and Si”, J. Appl. Phys, 88 (6), 3377 (2000).
25.J. D. Plummer, M. Deal, and P. B. Griffin, “Silicon VLSI technology Fundamentals, Practice and Modeling”, p.683.
26.H. Ono, T. Nakano, and T. Ohta, “Diffusion barrier effects of transition metals for Cu/M/Si multilayers (M=Cr, Ti, Nb, Mo, Ta, W)”, Appl. Phys. Lett. 64 (12), 1511 (1994).
27.Y. Ezer, J. Härkönen, V. Sokolov, J. Saarilahti, J. Kaitila, and P. Kuivalainen, “Diffusion barrier performance of thin Cr films in the Cu/Cr/Si structure”, Materials Research Bulletin, 33 (9), 1331 (1998).
28.F. Braud, J. Torres, J. Palleau, J. L. Mermet, and M. J. Mouche, “Ti-diffusion barrier in Cu-based metallization”, Appl. Surf. Sci., 91 (1-4), 251 (1995).
29.J. Y. Lee, S. R. Jeon, and J. W. Park, “Effect of deposition conditions on the physical and electrical properties of reactive sputtered molybdenum nitride film”, J. Mater. Sci. Lett., 15 (17), 1495 (1996).
30.K. Sakaki, H. Miyake, S. Shinkai, Y. Abe and H. Yanagisawa, “Realization of Cu(111) single-oriented state on SiO2 by annealing Cu-Zr film and the thermal stability of Cu-Zr/ZrN/Zr/Si contact system”, Jpn. J. Appl. Phys., part1, 40 (7), 4661 (2001).
31.T. Nitta, T. Ohmi, M. Otsuki, T. Takewaki and T. Shibata, “Electrical Properties of Giant-Grain Copper Thin Films Formed by a Low Kinetic Energy Particle Process”, J. Electrochem. Soc., 139 (3), 922 (1992).
32.K. Holloway, P. M. Fryer, C. Cabral, Jr., J. M. E. Harper, P. J. Bailey and K. H. Kelleher, “Tantalum as a diffusion barrier between copper and silicon : Failure mechanism and effect of nitrogen additions”, J. Appl. Phys., 71 (11), 5433 (1992).
33.W. L. Yang, W.-F. Wu, D.-G. Liu, C.-C. Wu, and K. L. Ou, “Barrier capability of TaNx films deposited by different nitrogen flow rate against Cu diffusion in Cu/TaNx/n+-p junction diodes”, Solid-State Electronics, 45, 149 (2001).
34.J.-C. Chuang, S.-L. Tu, and M.-C. Chen, “Sputtered Cr and reactively sputtered CrNx serving as barrier layers against copper diffusion”, J. Electrochem. Soc., 145 (12), 4290 (1998).
35.S.-Q. Wang, I. J. Raaijmarkers, B. J. Burrow, S. Suthar, S. Redkar and K.-B. Kim, “Reactively sputtered TiN as a diffusion barrier between Cu and Si“, J. Appl. Phys., 68 (10), 5176 (1990).
36.M. Y. Kwak, D. H. Shin, T. W. Kang, and K. N. Kim, “Characteristics of WN diffusion barrier layer for copper metallization”, Physica Status SolidI A - Applied Research, 174 (1), R5-R6 (1999).
37.J. Li, J. W. Strane, S. W. Russell, S. Q. Hong, J. W. Mayer, T. K. Marais, C. C. Theron, and R. Pretorius, “Observation and prediction of first phase formation in binary Cu-metal thin films”, J. Appl. Phys., 72 (7), 2810 (1992).
38.K. Hieber, “Structural and electrical properties of Ta and Ta nitrides deposited by chemical vapor deposition”, Thin Solid Films, 24 (1), 157 (1974).
39.E. Kolawa, P. J. Pokala, J. S. Chen, R. P. Ruiz, and Marc A. Nicolet, “Sputtered Ta-Si-N diffusion barriers in Cu metallizations for Si”, IEEE Electron Device Letters, 12 (6), 321 (1991).
40.N. Kristensen, F. Ericson and J.-Å. Schweitz, and U. Smith, “Hole formation in thin aluminum films under controlled variation of strain and temperature”, Thin Solid Films, 197, 67 (1991).
41.T. P. Nolan, R. Sinclair, and R. Beyers, “Modeling of agglomeration in polycrystalline thin films: Application to TiSi2 on a silicon substrate” J. Appl. Phys., 71 (2), 720 (1992).
42.J. J. Rha and J. K. Park, “Agglomeration of TiSi2 thin film on (100) Si substrates”, J. Appl. Phys., 82 (6), 2933 (1997).
43.K. T. Miller, F. F. Lange, and D. B. Marshall, “The instability of polycrystalline thin films: Experiment and theory”, J. Mater. Res., 5 (1), 151 (1990).
44.J. J. Rha and J. K. Park, “Stability of the grain configurations of thin films – A model for agglomeration”, J. Appl. Phys., 82 (4), 1608 (1997).
45.J. C. Lin, C. S. Liu, S. L. Shue, C. H. Yu, and M. S. Liang, “The evaluation of the diffusion barrier performance of reactively sputtered TaNx Layers for copper metallization”, IEEE International Interconnect Technology Conference 2000, pp.191 –193.
46.L. Vitos, A. V. Ruban, H. L. Skriver, and J. Kollár, “The surface energy of metals”, Surface Science, 411, 186 (1998).
47.C. D. Wagner, W. M. Riggs, L. E. Davis, J. F. Moulder, and G. E. Muilenberg, “Handbook of X-ray Photoelectron Spectroscopy, (Perkin-Elmer Corporation, 1979).