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The mechanical properties of freestanding electroplated Cu thin films

Published online by Cambridge University Press:  01 June 2006

Y. Xiang ,
T.Y. Tsui  and
J.J. Vlassak
Y. Xiang
Affiliation:
Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
T.Y. Tsui
Affiliation:
Texas Instruments, Inc., Dallas, Texas 75243
J.J. Vlassak*
Affiliation:
Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
*
a) Address all correspondence to this author. e-mail: vlassak@esag.deas.harvard.edu
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Abstract

The plane-strain bulge test is used to investigate the mechanical behavior of freestanding electroplated Cu thin films as a function of film thickness and microstructure. The stiffness of the films increases slightly with decreasing film thickness because of changes in the crystallographic texture and the elastic anisotropy of Cu. Experimental stiffness values agree well with values derived from single-crystal elastic constants and the appropriate orientation distribution functions. No modulus deficit is observed. The yield stress of the films varies with film thickness and heat treatment as a result of changes in the grain size of the films. The yield stress follows typical Hall-Petch behavior if twins are counted as distinct grains, indicating that twin boundaries are effective barriers to dislocation motion. The Hall-Petch coefficient is in good agreement with values reported for bulk Cu. Film thickness and crystallographic texture have a negligible effect on the yield stress of the films.

Keywords

CuFilmStress/strain relationship
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 6 , June 2006 , pp. 1607 - 1618
Copyright
Copyright © Materials Research Society 2006

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References

REFERENCES

1.Vinci, R.P., Vlassak, J.J.: Mechanical behavior of thin films. Annu. Rev. Mater. Sci. 26, 431 (1996).CrossRefGoogle Scholar
2.Nix, W.D.: Mechanical properties of thin films. Metall. Trans. A 20, 2217 (1989).CrossRefGoogle Scholar
3.Arzt, E.: Size effects in materials due to microstructural and dimensional constraints: A comparative review. Acta Mater. 46, 5611 (1998).CrossRefGoogle Scholar
4.Triantafyllidis, N., Aifantis, E.C.: A gradient approach to localization of deformation. 1. Hyperelastic materials. J. Elast. 16, 225 (1986).CrossRefGoogle Scholar
5.Aifantis, E.C.: Gradient deformation models at nano, micro, and macro scales. J. Eng. Mater. Technol. 121, 189 (1999).CrossRefGoogle Scholar
6.Fleck, N.A., Muller, G.M., Ashby, M.F., Hutchinson, J.W.: Strain gradient plasticity: Theory and experiment. Acta Metall. 42, 475 (1994).CrossRefGoogle Scholar
7.Fleck, N.A., Hutchinson, J.W.: A reformulation of strain gradient plasticity. J. Mech. Phys. Solids 49, 2245 (2001).CrossRefGoogle Scholar
8.Fleck, N.A., Hutchinson, J.W.: Strain gradient plasticity. Adv. Appl. Mech. 33, 295 (1997).CrossRefGoogle Scholar
9.Fleck, N.A., Hutchinson, J.W.: A phenomenological theory for strain gradient effects in plasticity. J. Mech. Phys. Solids 41, 1825 (1993).CrossRefGoogle Scholar
10.Nicola, L., Van der Giessen, E., Needleman, A.: Discrete dislocation analysis of size effects in thin films. J. Appl. Phys. 93, 5920 (2003).CrossRefGoogle Scholar
11.Needleman, A., Van der Giessen, E.: Discrete dislocation and continuum descriptions of plastic flow. Mater. Sci. Eng. A 309, 1 (2001).CrossRefGoogle Scholar
12.Dieter, G.E.: Mechanical Metallurgy, 3rd ed. (McGraw-Hill, New York, 1986), p. 287.Google Scholar
13.Spaepen, F., Yu, D.Y.W.: A comparison of the strength of multilayers, thin films and nanocrystalline compacts. Scripta Mater. 50, 729 (2004).CrossRefGoogle Scholar
14.Haque, M.A., Saif, M.T.A.: Mechanical behavior of 30-50 mn thick aluminum films under uniaxial tension. Scripta Mater. 47, 863 (2002).CrossRefGoogle Scholar
15.Schiotz, J., Di Tolla, F.D., Jacobsen, K.W.: Softening of nanocrystalline metals at very small grain sizes. Nature 391, 561 (1998).CrossRefGoogle Scholar
16.Shan, Z.W., Stach, E.A., Wiezorek, J.M.K., Knapp, J.A., Follstaedt, D.M., Mao, S.X.: Grain boundary-mediated plasticity in nanocrystalline nickel. Science 305, 654 (2004).CrossRefGoogle ScholarPubMed
17.Huang, H.B., Spaepen, F.: Tensile testing of free-standing Cu, Ag and Al thin films and Ag/Cu multilayers. Acta Mater. 48, 3261 (2000).CrossRefGoogle Scholar
18.Yu, D.Y.W., Spaepen, F.: The yield strength of thin copper films on Kapton. J. Appl. Phys. 95, 2991 (2004).CrossRefGoogle Scholar
19.Kalkman, A.J., Verbruggen, A.H., Janssen, G.C.A.M.: Young's modulus measurements and grain boundary sliding in freestanding thin metal films. Appl. Phys. Lett. 78, 2673 (2001).CrossRefGoogle Scholar
20.Read, D.T., Cheng, Y.W., Geiss, R.: Morphology, microstructure, and mechanical properties of a copper electrodeposit. Microelectron Eng. 75, 63 (2004).CrossRefGoogle Scholar
21.Read, D.T., Cheng, Y.W., Keller, R.R., McColskey, J.D.: Tensile properties of free-standing aluminum thin films. Scripta Mater. 45, 583 (2001).CrossRefGoogle Scholar
22.Espinosa, H.D., Prorok, B.C., Peng, B.: Plasticity size effects in free-standing submicron polycrystalline FCC films subjected to pure tension. J. Mech. Phys. Solids 52, 667 (2004).CrossRefGoogle Scholar
23.Haque, M.A., Saif, M.T.A.: Deformation mechanisms in free-standing nanoscale thin films: A quantitative in situ transmission electron microscope study. Proc. Natl. Acad. Sci. USA 101, 6335 (2004).CrossRefGoogle ScholarPubMed
24.Xiang, Y., Chen, X., and Vlassak, J.J.: The mechanical properties of electroplated Cu thin films measured by means of the bulge test technique, in Thin Films: Stresses and Mechanical Properties IX edited by Ozkan, C.S., Freund, L.B., Cammarata, R.C., and Gao, H. (Mater. Res. Soc. Symp. Proc. 695, Warrendale, PA, 2002), p. 189.Google Scholar
25.Xiang, Y., Vlassak, J.J., Perez-Prado, M.T., Tsui, T.Y., and McKerrow, A.J.: The effects of passivation layer and film thickness on the mechanical behavior of freestanding electroplated Cu thin films with constant microstructure, in Thin Films—Stresses and Mechanical Properties X edited by Corcoran, S.G., Joo, Y-C., Moody, N.R., and Suo, Z. (Mater. Res. Soc. Symp. Proc. 795, Warrendale, PA, 2004), p. 417.Google Scholar
26.Lee, H.J., Cornella, G., Bravman, J.C.: Stress relaxation of free-standing aluminum beams for microelectromechanical systems applications. Appl. Phys. Lett. 76, 3415 (2000).CrossRefGoogle Scholar
27.Xiang, Y., Chen, X., Vlassak, J.J.: Plane-strain bulge test for thin films. J. Mater. Res. 20, 2360 (2005).CrossRefGoogle Scholar
28.Xiang, Y., Vlassak, J.J.: Bauschinger effect in thin metal films. Scripta Mater. 53, 177 (2005).CrossRefGoogle Scholar
29.Flinn, P.A.: Measurement and interpretation of stress in copper-films as a function of thermal history. J. Mater. Res. 6, 1498 (1991).CrossRefGoogle Scholar
30.Thouless, M.D., Gupta, J., Harper, J.M.E.: Stress development and relaxation in copper-films during thermal cycling. J. Mater. Res. 8, 1845 (1993).CrossRefGoogle Scholar
31.Keller, R., Baker, S.P., Arzt, E.: Quantitative analysis of strengthening mechanisms in thin Cu films: Effects of film thickness, grain size, and passivation. J. Mater. Res. 13, 1307 (1998).CrossRefGoogle Scholar
32.Spolenak, R., Volkert, C.A., Takahashi, K., Fiorillo, S., Miner, J., and Brown, W.L.: Mechanical properties of electroplated copper thin films, in Thin Films—Stresses and Mechanical Properties VIII edited by Vinci, R., Kraft, O., Moody, N., Besser, P., and Shaffer, E., II (Mater. Res. Soc. Symp. Proc. 594, Warrendale, PA, 2000), p. 63.Google Scholar
33.Palatnik, L.S., Llinskii, A.I.: The strength of vacuum condensates of copper. Sov. Phys. Solid State 3, 2053 (1962).Google Scholar
34.Lawley, A., Schuster, S.: Tensile behavior of copper foils prepared from rolled material. Trans. Metall. Soc. AIME 230, 27 (1964).Google Scholar
35.Oding, I.A., Aleksanyan, I.T.: Mechanical properties of copper films. Sov. Phys. Dokl. 8, 818 (1964).Google Scholar
36.Leidheiser, H., Sloope, B.W.: Mechanical properties of copper films. J. Appl. Phys. 41, 402 (1970).CrossRefGoogle Scholar
37.Keller, R.R., Phelps, J.M., Read, D.T.: Tensile and fracture behavior of free-standing copper films. Mater. Sci. Eng. A 214, 42 (1996).CrossRefGoogle Scholar
38.Read, D.T.: Tension-tension fatigue of copper thin films. Int. J. Fatigue 20, 203 (1998).CrossRefGoogle Scholar
39.Perez-Prado, M.T., Vlassak, J.J.: Microstructural evolution in electroplated Cu thin films. Scripta Mater. 47, 817 (2002).CrossRefGoogle Scholar
40.Gangulee, A.: Structure of electroplated and vapor-deposited copper films. J. Appl. Phys. 43, 867 (1972).CrossRefGoogle Scholar
41.Tomov, I.V., Stoychev, D.S., Vitanova, I.B.: Recovery and recrystallization of electrodeposited bright copper coatings at room temperature. 2. X-ray investigation of primary recrystallization. J. Appl. Electrochem. 15, 887 (1985).CrossRefGoogle Scholar
42.Lee, H., Nix, W.D., Wong, S.S.: Studies of the driving force for room temperature microstructure evolution in electroplated copper films. J. Vac. Sci. Technol. B 22, 2369 (2004).CrossRefGoogle Scholar
43.Vlassak, J.J., Nix, W.D.: A new bulge test technique for the determination of Young's modulus and Poisson's ratio of thin films. J. Mater. Res. 7, 3242 (1992).CrossRefGoogle Scholar
44.Hong, S.H., Chung, K.H., Lee, C.H.: Effects of hot extrusion parameters on the tensile properties and microstructures of SiCw-2124Al composites. Mater. Sci. Eng. A 206, 225 (1996).CrossRefGoogle Scholar
45.Gao, H., Zhang, L., Nix, W.D., Thompson, C.V., Arzt, E.: Crack-like grain-boundary diffusion wedges in thin metal films. Acta Mater. 47, 2865 (1999).CrossRefGoogle Scholar
46.Joo, Y.C., Hwang, S.J., Park, H.: The effect of grain boundary characteristics on microstructure and stress void evolution in electroplated and sputtered cu films. Mater. Sci. Forum 426–432, 3481 (2003).CrossRefGoogle Scholar
47.Barrett, C.R., Nix, W.D., Tetelman, A.S.: The Principles of Engineering Materials (Prentice-Hall, Englewood Cliffs, NJ, 1973).Google Scholar
48.Simmons, G., Wang, H.: Single Crystal Elastic Constants and Calculated Aggregate Properties: A Handbook, 2nd ed. (MIT Press, Cambridge, MA, 1970).Google Scholar
49.Tada, H., Paris, P.C., Irwin, G.R.: The Stress Analysis of Cracks Handbook (Del Research Corporation, Hellertown, PA, 1973).Google Scholar
50.Phillips, M.A., Spolenak, R., Tamura, N., Brown, W.L., MacDowell, A.A., Celestre, R.S., Padmore, H.A., Batterman, B.W., Arzt, E., Patel, J.R.: X-ray microdiffraction: Local stress distributions in polycrystalline and epitaxial thin films. Microelectron. Eng. 75, 117 (2004).CrossRefGoogle Scholar
51.Lu, L., Shen, Y.F., Chen, X.H., Qian, L.H., Lu, K.: Ultrahigh strength and high electrical conductivity in copper. Science 304, 422 (2004).CrossRefGoogle ScholarPubMed
52.Youngdahl, C.J., Weertman, J.R., Hugo, R.C., Kung, H.H.: Deformation behavior in nanocrystalline copper. Scripta Mater. 44, 1475 (2001).CrossRefGoogle Scholar
53.Armstrong, R., Codd, I., Douthwaite, R.M., Petch, N.J.: Plastic deformation of polycrystalline aggregates. Philos. Mag. 7, 45 (1962).CrossRefGoogle Scholar
54.Bunge, H-J.: Texture Analysis in Materials Science: Mathematical Methods (Butterworths, London, 1982).Google Scholar
55.Kocks, U.F.: Relation between polycrystal deformation and single-crystal deformation. Metall. Trans. 1, 1121 (1970).CrossRefGoogle Scholar