電遷移效應對銅薄膜表面粗糙度影響之研究｜國立清華大學博碩士論文庫

簡易檢索 / 詳目顯示

回結果列表

研究生：	詹宗晟
論文名稱：	電遷移效應對銅薄膜表面粗糙度影響之研究 A Study of Effect of Electromigration on Surface Roughness of Copper Thin Film
指導教授：	廖建能
口試委員:
學位類別：	碩士 Master
系所名稱：	工學院 - 材料科學工程學系 Materials Science and Engineering
論文出版年：	2008
畢業學年度：	96
語文別：	英文
論文頁數：	57
中文關鍵詞：	銅導線、平坦化、電遷移、銅製程、表面粗糙度
外文關鍵詞：	copper interconnect, planarization, electromigration, copper metallization, surface roughness
相關次數：	點閱：2 下載：0
分享至:	分享至facebook 分享至twitter

查詢本校圖書館目錄查詢臺灣博碩士論文知識加值系統勘誤回報

在銅製程中，銅晶種層的表面粗糙度對於之後的電鍍銅導線性質會有很密切的影響。隨著電子元件的不斷縮小，到了45奈米製程節點，銅晶種層的厚度會下降到30-50奈米且其表面粗糙度需低於1奈米。然而在本實驗中，銅薄膜在200 °C退火1分鐘之後，其表面粗糙度會高達7.5奈米。在電鍍過程中，ㄧ個表面粗糙的銅晶種層會在銅晶種層跟電鍍銅導線之間產生孔洞，進而造成元件可靠度下降的問題。在本研究中，我們利用電致遷移的方法，試圖改善銅薄膜的表面粗糙度。藉由原子力顯微鏡的分析結果，我們發現在通電流30分鐘之後，銅薄膜的表面粗糙度由原本的7.5奈米下降至4奈米，在通電流10小時之後，銅薄膜的表面粗糙度更進一步下降至1.4奈米，這個現象可藉由表面晶粒薄化(grain thinning)來解釋。另外，一般來講，施加交流電通過金屬薄膜並不會造成任何電致遷移的現象發生，然而在本實驗中，我們發現施加交流電通過銅薄膜也可讓其粗糙度下降，這部份推測與棘輪作用(ratchet effect)有關。

For conventional copper (Cu) damascene processes employed in integrated-circuits fabrication technology, a seed layer is required prior to electroplating of copper metallization. As a result, the surface roughness of the seed layer is expected to affect the structure and quality of the electroplated Cu layer. For 45 nm technology node, the thickness of Cu seed layer will be 30-50 nm with less than 1 nm surface roughness. However, the surface roughness of Cu films after annealing at 200 °C for 1 minute would be 7.5 nm. A rough Cu surface would cause voiding problem between Cu seed layer and electroplated Cu, leading to electromigration reliability issue. In the present study, we have proposed a method to improve the surface roughness of copper thin films by electric current induced surface smoothing. Due to fast surface diffusion of copper atoms, the surface morphology of copper thin film can be modified by electrical current induced atomic migration. Our results show that the surface morphology and film texture of the electrically stressed Cu thin films change notably with time according to the atomic force microscopy (AFM) and X-ray diffraction (XRD) analysis. The roughness of copper thin film was found to improve from the initial 7.5 nm to 4 nm after 30-minute electrical current stressing, and eventually down to 1.4 nm after 10 hours of electrical current stressing. In general, no long range mass transport is expected for metal films stressed by alternating electrical current. However, the surface roughness of Cu films is reduced after alternating electrically stressing. The mechanism of electric current induce surface smoothing is speculated to be related to the ratchet effect.

致謝    I
Abstract in Chinese    II
Abstract……………………………………………………………………………II
Contents    .......IV
List of Figures    VII

Chapter 1  Introduction    1
1.1  Motivation    1
1.2  Objective    2
1.3  Organization of thesis    3

Chapter 2  Literature review    4
2.1  Seed layer depositing method    4
2.1.1  Seed layer deposited by chemical vapor deposition    6
2.1.2  Seed layer deposited by atomic layer deposition    8
2.1.3  Seed layer deposited by electroless deposition    8
2.1.4  Diffusion barrier / adhesion layer as seed layer    9
2.2  Roughening mechanism during deposition    10
2.3  The nucleation extrusion zones    13
2.4  Electromigration physics    14
2.4.1  Theory of electromigration    16
2.4.2  Effect of microstructure on Cu electromigration    19
2.4.3  Application of electromigration    23

Chapter 3  Experimental procedure    ……..25
3.1  Specimen preparation    25
3.2  Experimental setup    26
3.3  Analyses techniques    28
3.3.1  X-ray diffractometry    28
3.3.2  Atomic force microscopy    28

Chapter 4  Results and discussions    30
4.1  Evolution of surface morphology of Cu thin film during annealing    30
4.2  Effect of electrical current stressing on surface morphology and
     texture of Cu films………………………………………………..…..37
  4.2.1  Evolution of surface morphology and texture of Cu films after
        electrical current stressing……………………..……………........37
  4.2.2  Grain thinning mechanism…………….………………….…........41
  4.2.3  Effect of alternating electrical current on surface morphology…..45

Chapter 5  Conclusions    50
5.1  Conclusions………………….………….…………….………….........50
5.2  Future works………………………50

References    52
List of Figures
Figure 2-1   Types of evolution in Cu damascene plating profile    5
Figure 2-2   SEM photographs of filling experiments in different filling condition,
           (A) Voided filling, (B) Void-free filling, and (C) Seam type voided
           filling    6
Figure 2-3   Comparison of conventional and seedless barrier processes    10
Figure 2-4   STM images of the first derivative measured for deposition at different
           thicknesses and temperature, 299 K    12
Figure 2-5   Schematic of the cross-section of a vicinal surface (lower panel)
           containing two monatomic steps and the asymmetric lattice potential
           (upper panel) experienced by the atoms (gray circles) diffusing on this
           surface. Note that a non-zero Schwoebel barrier, Eb, is necessary to
           break the spatial symmetry of the potential    12
Figure 2-6   A schematic representation of the deformation of the electric field
           around a granular defect on a substrate……………………………….    .14
Figure 2-7   TEM image showing a large EM-induced void at the cathode end of a
           60nm wide Cu wire    15
Figure 2-8   TEM image showing void at the cathode end and extrusion at the anode
           end for a Cu wire under electrical current stressing    15
Figure 2-9   The dependence of EM lifetime on microstructure of Al-based
           interconnects    22
Figure 2-10  The schematic diagrams of void growth mechanisms: (a) edge
           displacement and (b) surface grain thinning. The direction of electron
           flow is from right to left. Arrows with the dotted lines show the
           migration of Cu atoms    22
Figure 2-11  (a) Al nanowire from a 0.5-μm-square slot penetrating the passivation
           layer and (b) Al nanowire from a 0.2-μm-square slot not penetrating the
           passivation layer    24
Figure 2-12  Unzipping model of evolution of a nanogap during FCE. (a) Starting
           with the initial wire, an edge atom is thermally excited. (b) This atom is
           easily transported away by the applied current along the high-mobility
           [110] directions. (c) The edge vacancy allows adjacent atoms to easily
           electromigrate and jump to the edge due to their reduced number of
           nearest neighbors. (d) The edge is thus unstable once theunzipping of a
           layer begins    24
Figure 3-1   The scheme of experimental process    26
Figure 3-2   Schematic diagram of an electric current passing through the Cu stripe
           using electrical probe    27
Figure 4-1   AFM image showing the surface morphology and surface roughness of
           as-deposited Cu thin film    34
Figure 4-2   AFM image showing the surface morphology of Cu thin film after
           annealing for 1 minute at different temperature. (a) 200°C, (b) 250°C,
           (c)300°C, (d) 400°C    34
Figure 4-3   AFM image showing the surface morphology of Cu thin film after
annealing for 2 minutes at different temperature. (a) 200°C, (b) 250°C,
(c) 300°C, (d) 400°C    35
Figure 4-4   Texture map calculated with surface/interface and elastic strain energy
for Cu-film resulting from grain growth at temperature Tgg in Cu films
of thickness h, deposited at Tdep    36
Figure 4-5   Schematic diagram of grain boundary migration due to Cu atoms
 diffuse from (110)-textured grain to (111)-textured grain driven by
surface energy minimization…………………………………………    36
Figure 4-6   AFM images showing the surface morphology of the Cu thin film after
electrical current stressing for different times. (a) none ; (b) 10 min ; (c)
30min ; (d) 1hr ; (e) 5hrs; (f) 10hrs    39
Figure 4-7   The surface roughness values of Cu thin film after electrical current
stressing for different times    40
Figure 4-8   The X-ray diffraction spectra for a Cu thin film at different stages
during electric current stressing    40
Figure 4-9   AFM image showing the surface morphology of annealed Cu thin film
after annealing at 100 °C in 1 hour again. (a) annealed at 200 °C in
2mins ;(b) the same as (a) except additionally annealing at 100 °C in 1
hour again ;(c) annealed at 250 °C in 2mins ;(d) the same as (c) except
additionally annealing at 100 °C in 1 hour again    41
Figure 4-10   Schematic diagram of grain thinning mechanism    44
Figure 4-11   Shematic diagram of grain thinning mechanism in {111}-oriented
grain    44
Figure 4-12   AFM image showing the surface morphology of Cu thin film after
stressing electrical current. (a) without stressing; (b) with stressing an
direct current in 1 hour ;(c) with stressing an alternating current with
100Hz in 1 hour ;(d) with stressing an alternating current with 1000Hz
in 1 hour    47
Figure 4-13   AFM image showing the surface morphology of Cu thin film after
stressing electrical current. (a) without stressing; (c) with stressing an
direct current in 1 hour; (e) with stressing an alternating current with
1000Hz in 1 hour; (b), (d), and (f) are scan lines indicated in (a), (c),
and(e), respectively    48
Figure 4-14   Ratchet effect. (a) Shoewel barrier potential for a given stepped
surface. (b) When an external field is applied, the minimum located at
points b (descending surface slope) are deeper than that those at a
(ascending surface slope). (c) When reversing the electric field, the
minimum distribution also changes, and now, the deeper minimum is
located at point b’    49

                                

1. K. I. Popov, S. S. Djokic, and B. N. Grgur, “Fundamental aspects of electrometallurgy”, New York, Kluwer Academic / Plenum Publishers
2. International Technology Roadmap for Semiconductors (ITRS)
3. G. Nana and L.E Camilletti , “Modeling of chemical-mechanical polishing – a review”, IEEE Trans. Semicond. Manuf. 8, 382 (1995)
4. M. H. Su and J. M. Lu “Investigation of Ar incident energy and Ar incident angle effects on surface roughness of Cu metallic thin film in ion assisted deposition”, Comput. Mater. Sci. 38, 386 (2006)
5. H. Han, Y. Zoo, J. W. Mayer, and T. L. Alford, “Improved surface morphology and texture of Ag films on indium tin oxide via Cu additions”, J. Appl. Phys. 102, 036101 (2007)
6. R. Rosenberg and M. Ohring, “Void formation and growth during electromigration in thin films”, J. Appl. Phys. 42, 5671 (1971)
7. I. Derenyi, C. Lee, and A.Z. Barabasi, “Ratchet effect in surface electromigration： smoothing surfaces by an ac field”, Phys. Rev. Lett. 80, 1473 (1998)
8. R. Rosenberg, D. C. Edelstein, C.-K. Hu, and K. P. Rodbell, “Copper metallization for high performance silicon technology”, Annu. Rev. Mater. Sci. 30, 229 (2000).
9. O. van der Straten, Y. Zhu, K. Dunn, E. T. Eisenbraun, and A. E. Kaloyeros, “Atomic layer deposition of tantalum nitride for ultrathin liner applications in advanced copper metallization schemes”, J. Mater. Res. 19, 447 (2004).
10. P. C. Andricacos, C. Uzoh, J. O. Dukovic, J. Horkans, H. Deligianni, “Damascene copper electroplating for chip interconnections”, IBM J. Res. Develop. 42, 567 (1998)
11. 吳邦豪, “非等向性電鍍銅於積體電路內連線之研究”, 國立清華大學博士論文 (2003)
12. M. Stangl, A. Fletcher, J. Acker, H. Wendrock, and K. Wetzig, “Influence of Ta-based diffusion barriers on the microstructure of Copper thin films”, J. Electron. Mater. 36, 1625 (2007)
13. H. Lee and S. D. Lopatin, “The influence of barrier types on the microstructure and electromigration characteristics of electroplated Cu”, Thin Solid Films 492, 279 (2005)
14. Y. S. Kim and Y. Shimogaki, “X-ray photoelectron spectroscopic characterization of the adhesion behavior of chemical vapor deposited copper films”, J. Vac. Sci. Technol. A 19, 2642 (2001)
15. R. Kroger, M. Eizenberg, D. Cong, N. Yoshida, L. Y. Chen, S. Ramaswami, and D. Carl, “Properties of copper films prepared by chemical vapor deposition for advanced metallization of microelectronic devices”, J. Electrochem. Soc. 146, 3248 (1999)
16. M. W. Lane, C. E. Murray, F. R. McFeely, P. M. Vereecken, and R. Rosenberg, “Liner materials for direct electrodeposition of Cu”, Appl. Phys. Lett. 83, 2330 (2003)
17. M. Ohring, The Materials Science of Thin Films, Academic Press, London, 1992
18. H. Kim, “The application of atomic layer deposition for metallization of 65 nm and beyond”, Surf. Coat. Technol. 200, 3104 (2006)
19. R. Puurunen, “Surface chemistry of atomic layer deposition: A case study for the
Trimethylaluminum / water process”, J. Appl. Phys. 97, 121301 (2005)
20. L. Wu, and E. Eisenbraun, “Hydrogen plasma-enhanced atomic layer deposition of copper thin films”, J. Vac. Sci. Technol. B 25, 2581 (2007)
21. Z. Li, S. T. Barry, and R. G. Gordon, “Synthesis and characterization of copper(I) amidinates as precursors for atomic layer deposition (ALD) of copper metal”, Inorg. Chem. 44, 1728 (2005)
22. V. M. Dubin, “Selective electroless Ni-Cu(P) deposition for via hole filling and conductor pattern cladding in VLSI multilevel interconnection structures”, J. Electrochem. Soc. 139, 633 (1992)
23. T. P. Moffat, M. Walker, P. J. Chen, J. E. Bonevich, W. F. Egelhoff, L. Richter, C. Witt, T. Aaltonen, M. Ritala, M. Leskelä, and D. Josell, “Electrodeposition of Cu on Ru barrier layers for damascene processing”, J. Electrochem. Soc. 153, C37 (2006)
24. 張淑雅, “以無電鍍法研製銅內連線擋層Ni-W-P之研究”, 國立清華大學碩士論文 (2004)
25. J.-K. Zuo and J. F. Wendelken, “Evolution of mound morphology in reversible homoepitaxy on Cu (100)”, Phys. Rev. Lett. 78, 2791 (1997)
26. Z.-J. Liu and Y. G. Shen, “Roughening kinetics of thin films in the presence of both stress and Ehrlich–Schwobel barrier”, Appl. Phys. Lett. 74, 2945 (1999)
27. I. Der´enyi, “Application of the ratchet effect to improve material quality (reducing vortex density in superconductors and smoothing surfaces)”, Appl. Phys. A-Mater. Sci. Process. 75, 217 (2002)
28. Z. J. Liu, and Y. G. Shen, “Temperature effect on surface roughening of thin films”, Surf. Sci. 595, 20 (2005)
29. M. Gerardin, Compt. Rend. 53, 727 (1861)
30. J. W. Pyun, W. C. Beak, L. J. Zhang, J. Im, P. S. Ho, L. Smith, and G. Smith, “Electromigration behavior of 60 nm dual damascene Cu interconnects”, J. Appl. Phys. 102, 093516 (2007)
31. E. T. Ogawa, K. -D. Lee, V. A. Blaschke, and P. S. Ho, “Electromigration reliability issues in dual-damascene Cu interconnections”, IEEE Trans. Reliab. 51, 403 (2002).
32. W. Seith and H. Wever, Z. Elecktrochem. 59, 942 (1953)
33. V. B. Fiks, “Mechanism of ion mobility in metals”, Sov. Phys.-Solid State 1, 14 (1959)
34. H. B. Hungtington and A. R. Grone, “Current-induced marker motion in gold wires”, J. Phys. Chem. Solids 20, 76 (1961)
35. C. K. Hu, R. Rosenberg, and K. Y. Lee, “Electromigration path in Cu thin-film lines”, Appl. Phys. Lett. 74, 2945 (1999)
36. C. K. Hu, L. Gignac, and R. Rosenberg, “Electromigration of Cu/low dielectric constant interconnects”, Microelectron. Reliab. 46, 213 (2006)
37. S. J. Rothman and N. L. Peterson, “Isotope effect and divacancies for self-diffusion in copper”, Phys. Status Solidi 35, 305 (1969)
38. C. S. Hau-Riege, “An introduction to Cu electromigration”, Microelectron. Reliab. 44, 195 (2004)
39. J. R. Lloyd, J. Clemens, and R, Snede, “Copper metallization reliability”, Microelectron. Reliab. 39, 1595 (1999)
40. S. Vaidya, T. T. Sheng, and A. K. Sinha, “Linewidth dependence of electromigration in evaporated Al-0.5%Cu”, Appl. Phys. Lett. 36, 464 (1980)
41. Y. C. Joo and C. V. Thompson, “Analytical model for the grain structures of near-bamboo interconnects”, J. Appl. Phys. 76, 7339 (1994)
42. F. d’Heurle and I. Ames, “Electromigration in single-crystal aluminum films”, Appl. Phys. Lett. 16, 80 (1970)
43. S. Vaidya and A. K. Sinha, “Effect of texture and grain structure on electromigration in Al-0.5%Cu thin films”, Thin Solid Films 75, 253 (1981)
44. D. B. Knorr and D. P. Tracy, “Correlation of texture with electromigration behavior in Al metallization”, Appl. Phys. Lett. 16, 80 (1970)
45. K. N. Tu, “Recent advances on electromigration in very-large-scale-integration of interconnects”, J. Appl. Phys. 94, 5451 (2003)
46. C. Ryu, K. W. Kwon, A. L. S. Loke, H. Lee, T. Nogami, V. M. Dubin, R. A. Kavari, G. W. Ray, and S. S. Wong, “Microstructure and reliability of copper interconnects”, IEEE Trans. Electron. Devices 46, 1113 (1999)
47. M. Karimi and T. Tomkowski, “Diffusion of Cu on Cu surfaces”, Phys. Rev. B 52, 5364 (1995)
48. 陳冠嘉, “超高真空穿透式電子顯微鏡臨場觀察銅導線電遷移特性之研究”, 國立清華大學博士論文 (2008)
49. M. Saka and R. Ueda, “Formation of metallic nanowires by utilizing electromigration”, J. Mater. Res. 20, 2712 (2005)
50. D. R. Strachan, D. E. Johnston, B. S. Guiton, S. S. Datta, P. K. Davies, D. A. Bonnell, and A. T. Charlie Johnson, “Real-time TEM imaging of the formation of crystalline nanoscale gaps”, Phys. Rev. Lett. 100, 056805 (2008)
51. H. Park., A. K. L. Lim, A. P. Alivisatos, J. Park, and P. L. Mceuen, “Fabrication of metallic electrodes with nanometer separation by electromigration”, Appl. Phys. Lett. 75, 301 (1999)
52. D. E. Johnston, D. R. Strachan, and A. T. Charlie Johnson, “Parallel fabrication of nanogap electrodes”, Nano Lett. 7, 2774 (2007)
53. K. I. Bolotin, F. Kuemmeth, A. N. Pasupathy, and D. C. Ralph, “Metal-nanoparticle single-electron transistors fabricated using electromigration”, Appl. Phys. Lett. 84, 3154 (2004)
54. C. Kothandaraman, S. K. Iyer, and S. S. Iyer, “Electrically programmable fuse (eFUSE) using electromigration in silicides”, IEEE. Electron. Devices Lett. 23, 523 (2002)
55. C. V. Thompson and R. Carel, “Stress and grain growth in thin films”, J. Mech. Phys. Solids 44, 657 (1996)
56. N. J. Park and D. P. Field, “Predicting thickness dependent twin boundary formation in sputtered Cu films”, Scripta Mater. 54, 999 (2006)
57. Y. N. Wen and J. M. Zhang, “Surface energy calculation of the f.c.c. metals by using the MAEAM”, Solid State Commun. 144, 163 (2007)
58. L. H. Xu, D. Xu, S. Ratanaphan, K. N. Tu, N. Wang, J. H. L. Pang, and J. M. Miao, “Structure and migration of (112) step on (111) twin boundaries in nano-crystalline copper”, Acta Mater. Submitted.
59. A. Gladkikh, M. Karpovski, A. Palevski, and Y. S. Kaganovski, “Effect of microstructure on electromigration kinetics in Cu lines”, J. Phys. D: Appl. Phys. 31, 1626 (1998)
60. P. J. de Pablo, J. Colchero, J. Go´mez-Herrero, A. Asenjo, M. Luna, P. A. Serena, and A. M. Baro, “Ratchet effect in surface electromigration detected with scanning force microscopy in gold micro-stripes”, Surf. Sci. 464, 123 (2000)

全文公開日期本全文未授權公開 (校內網路)
全文公開日期本全文未授權公開 (校外網路)

簡易檢索 / 詳目顯示

相關論文