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Brittle-to-ductile transition in ultrathin Ta/Cu film systems

  • Patric A. Gruber (a1), Eduard Arzt (a2) and Ralph Spolenak (a3)

Abstract

Current semiconductor technology demands the use of compliant substrates for flexible integrated circuits. However, the maximum total strain of such devices is often limited by the extensibility of the metallic components. Although cracking in thin films is extensively studied theoretically, little experimental work has been carried out thus far. Here, we present a systematic study of the cracking behavior of 34- to 506-nm-thick Cu films on polyamide with 3.5-to 19-nm-thick Ta interlayers. The film systems have been investigated by a synchrotron-based tensile testing technique and in situ tensile tests in a scanning electron microscope. By relating the energy release during cracking obtained from the stress-strain curves to the crack area, the fracture toughness of the Cu films can be obtained. It increases with Cu film thickness and decreases with increasing Ta film thickness. Films thinner than 70 nm exhibit brittle fracture, indicating an increasing inherent brittleness of the Cu films.

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Corresponding author

a) Present address: Universität Karlsruhe, Institut für Zuverlässigkeit von Bauteilen und Systemen, D-76131 Karlsruhe, Germany.
b) Address all correspondence to this author. e-mail: ralph.spolenak@mat.ethz.ch

References

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1Chen, Y.Au, J.Kazlas, P.Ritenour, A.Gates, H. and McCreary, M.: Flexible active-matrix electronic ink display. Nature 423, 136 (2003).
2Gelinck, G.H., Edzer, H.Huitema, A.Veenendaal, E.V., E. van Cantatore, Schrijnemakers, L.Putten, J. van der, Geuns, T.C.T., Beenhakkers, M.Giesbers, J.B., Hiusman, B.H., Meijer, E.J., Benito, E.M., Touwslager, F.J., Marsman, A.W., van Rens, B.J.E., and Leeuw, D.M. De: Flexible active-matrix displays and shift registers based on solution-processed organic transistors. Nat. Mater. 3, 106 (2004).
3Post, E.R., Orth, M.Russo, P.R., and Gershenfeld, N.: E-broidery: Design and fabrication of textile-based computing. IBM Syst. J. 39, 840 (2000).
4Bonderover, E. and Wagner, S.: A woven inverter circuit for e-textile applications. IEEE Electron Device Lett. 25, 295 (2004).
5Wagner, S.Lacour, S.P., Jones, J.Hsu, P.H.I., Sturm, J.C., Li, T. and Suo, Z.G.: Electronic skin: Architecture and components. Physica E 25, 326 (2004).
6Meyer, J.U.: Retina implant—A bioMEMS challenge. Sens. Actuators, A 97-98, 1 (2002).
7Stett, A.Egert, U.Guenther, E.Hofmann, F.Meyer, T.Nisch, W. and Haemmerle, H.: Biological application of microelectrode arrays in drug discovery and basic research. Anal. Bioanal. Chem. 377, 486 (2003).
8Zhang, S.Sun, D.Fu, Y.Q., and Du, H.J.: Toughness measurement of thin films: A critical review. Surf. Coat. Technol. 198, 74 (2005).
9Handge, U.A., Leterrier, Y.Rochat, G.Sokolov, I.M., and Blumen, A.: Two scaling domains in multiple cracking phenomena. Phys. Rev. E: Stat. Phys., Plasmas, Fluids, Relat. Interdiscip. Topics 62, 7807 (2000).
10Rochat, G.Leterrier, Y.Fayet, P. and Manson, J.A.E.: Mechanical analysis of ultrathin oxide coatings on polymer substrates in situ in a scanning electron microscope. Thin Solid Films 437, 204 (2003).
11Xiang, Y.Li, T.Suo, Z.G., and Vlassak, J.J.: High ductility of a metal film adherent on a polymer substrate. Appl. Phys. Lett. 87, 61910 (2005).
12Heinrich, M.Gruber, P.Orso, S.Handge, U.A., and Spolenak, R.: Dimensional control of brittle nanoplatelets. A statistical analysis of a thin film cracking approach. Nano Lett. 6, 2026 (2006).
13Handge, U.A.: Analysis of a shear-lag model with nonlinear elastic stress transfer for sequential cracking of polymer coatings. J. Mater. Sci. 37, 4775 (2002).
14Leterrier, Y.Boogh, L.Andersons, J. and Manson, J.A.: Adhesion of silicon oxide layers on poly(ethylene terephthalate). I. Effect of substrate properties on coating's fragmentation process. J. Polym. Sci., Part B: Polym. Phys. 35, 1449 (1997).
15Leterrier, Y.Andersons, J.Pitton, Y. and Manson, J.A.: Adhesion of silicon oxide layers on poly(ethylene terephthalate). II. Effect of coating thickness on adhesive and cohesive strengths. J. Polym. Sci., Part B: Polym. Phys. 35, 1463 (1997).
16Jansson, N.E., Leterrier, Y. and Manson, J.A.E.: Modeling of multiple cracking and decohesion of a thin film on a polymer substrate. Eng. Fract. Mech. 73, 2614 (2006).
17Jansson, N.E., Leterrier, Y.Medico, L. and Manson, J.A.E.: Calculation of adhesive and cohesive fracture toughness of a thin brittle coating on a polymer substrate. Thin Solid Films 515, 2097 (2006).
18Alaca, B.E., Selby, J.C., Saif, M.T.A., and Sehitoglu, H.: Biaxial testing of nanoscale films on compliant substrates: Fatigue and fracture. Rev. Sci. Instrum. 73, 2963 (2002).
19Chen, Z. and Gan, Z.H.: Fracture toughness measurement of thin films on compliant substrate using controlled buckling test. Thin Solid Films 515, 3305 (2007).
20Böhm, J., Gruber, P.Spolenak, R.Stierle, A.Wanner, A., and Arzt, E.: Tensile testing of ultrathin polycrystalline films: A synchrotronbased technique. Rev. Sci. Instrum. 75, 1110 (2004).
21Gruber, P.Böhm, J., Wanner, A.Sauter, L.Spolenak, R. and Arzt, E.: Size effect on crack formation in Cu/Ta and Ta/Cu/Ta thin film systems, in Nanoscale Materials and Modeling—Relations Among Processing, Mircostructure and Mechanical Properties, edited by Anderson, P.M., Foecke, T.Misra, A. and Rudd, R.E. (Mater. Res. Soc. Symp. Proc. 821, Warrendale, PA, 2004), P2.7.
22Gruber, P.Böhm, J., Onuseit, F.Wanner, A.Spolenak, R. and Arzt, E.: Size effects on yield strength and strain hardening for ultra thin Cu films with and without passivation: A study by synchrotron and bulge test techniques. Acta Mater. 56, 2318 (2008).
23BeuthJr, J.L..: Cracking of thin bonded films in residual tension. Int. J. Solids Struct. 29, 1657 (1992).
24Xia, Z.C. and Hutchinson, J.W.: Crack patterns in thin films. J. Mech. Phys. Solids 48, 1107 (2000).
25Beuth, J.L. and Klingbeil, N.W.: Cracking of thin films bonded to elastic-plastic substrates. J. Mech. Phys. Solids 44, 1411 (1996).
26Vlassak, J.J.: Channel cracking in thin films on substrates of finite thickness. Int. J. Fract. 119, 299 (2003).
27Begley, M.R. and Bart-Smith, H.: The electro-mechanical response of highly compliant substrates and thin stiff films with periodic cracks. Int. J. Solids Struct. 42, 5259 (2005).
28Begley, M.R., Bart-Smith, H., Scott, O.N., Jones, M.H., and Reed, M.L.: The electro-mechanical response of elastomer membranes coated with ultra-thin metal electrodes. J. Mech. Phys. Solids 53, 2557 (2005).
29Li, T.Huang, Z.Y., Suo, Z.Lacour, S.P., and Wagner, S.: Stretchability of thin metal films on elastomer substrates. Appl. Phys. Lett. 85, 3435 (2004).
30Li, T.Huang, Z.Y., Xi, Z.C., Lacour, S.P., Wagner, S. and Suo, Z.: Delocalizing strain in a thin metal film on a polymer substrate. Mech. Mater. 37, 261 (2005).
31Li, T. and Suo, Z.: Deformability of thin metal films on elastomer substrates. Int. J. Solids Struct. 43, 2351 (2006).
32Dundurs, J. and Bogy, D.B.: Edge-bonded dissimilar orthogonal elastic wedges under normal and shear loading. J. Appl. Mech. 36, 650 (1969).
33Hertzberg, R.W.: Deformation and Fracture Mechanics of Engineering Materials (John Wiley & Sons, NY, 1989), pp. 289294.
34Hsia, K.J., Suo, Z. and Yang, W.: Cleavage due to dislocation confinement in layered materials. J. Mech. Phys. Solids 42, 877 (1994).
35Moody, N.R., Medlin, D.Boehme, D. and Norwood, D.P.: Film thickness effects on the fracture of tantalum nitride on aluminum nitride thin film systems. Eng. Fract. Mech. 61, 107 (1998).
36Wellner, P.Kraft, O.Dehm, G.Andersons, J. and Arzt, E.: Channel cracking of b-NiAl thin films on Si substrates. Acta Mater. 52, 2325 (2004).

Keywords

Brittle-to-ductile transition in ultrathin Ta/Cu film systems

  • Patric A. Gruber (a1), Eduard Arzt (a2) and Ralph Spolenak (a3)

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