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Mechanical properties of porous and fully dense low-κ dielectric thin films measured by means of nanoindentation and the plane-strain bulge test technique

Published online by Cambridge University Press:  01 February 2006

Y. Xiang ,
X. Chen ,
T.Y. Tsui ,
J-I. Jang  and
J.J. Vlassak
Y. Xiang
Affiliation:
Division of Engineering and Applied Sciences, Harvard University, Cambridge, Massachusetts 02138
X. Chen
Affiliation:
Department of Civil Engineering and Engineering Mechanics, Columbia University, New York, New York 10027
T.Y. Tsui
Affiliation:
Texas Instruments Inc., Dallas, Texas 75243
J-I. Jang
Affiliation:
Department of Materials Science and Engineering, Hanyang University, Seoul 133-791, South Korea
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

We report on the results of a comparative study in which the mechanical response of both fully dense and porous low-κ dielectric thin films was evaluated using two different techniques: nanoindentation and the plane-strain bulge test. Stiffness values measured by nanoindentation are systematically higher than those obtained using the bulge test technique. The difference between the measurements is caused by the Si substrate, which adds significantly to the contact stiffness in the indentation measurements. Depending on the properties of the coatings, the effect can be as large as 20%, even if the indentation depth is less than 5% of the film thickness. After correction of the nanoindentation results for the substrate effect using existing models, good agreement is achieved between both techniques. The results further show that densification of porous material under the indenter does not affect stiffness measurements significantly. By contrast, nanoindentation hardness values of porous thin films are affected by both substrate and densification effects. It is possible to eliminate the effect of densification and to extract the yield stress of the film using a model for the indentation of porous materials proposed by the authors. After correcting for substrate and densification effects, the nanoindentation results are in close agreement with the bulge test measurements. The results of this comparative study validate the numerical models proposed by Chen and Vlassak for the substrate effect and by Chen et al. for the densification effect.

Keywords

Mechanical propertiesNanoindentationThin film
Type
Articles
Information
Journal of Materials Research , Volume 21 , Issue 2 , February 2006 , pp. 386 - 395
Copyright
Copyright © Materials Research Society 2006

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References

REFERENCES

1.Morgen, M., Ryan, E.T., Zhao, J.H., Hu, C., Cho, T.H. and Ho, P.S.: Low-dielectric constant materials for ULSI interconnects. Annu. Rev. Mater. Sci. 30, 645 (2000).Google Scholar
2.Maex, K., Baklanov, M.R., Shamiryan, D., Iacopi, F., Brongersma, S.H. and Yanovitskaya, Z.S.: Low-dielectric constant materials for microelectronics. J. Appl. Phys. 93, 8793 (2003).CrossRefGoogle Scholar
3.Volinsky, A.A., Vella, J.B. and Gerberich, W.W.: Fracture toughness, adhesion and mechanical properties of low-K dielectric thin films measured by nanoindentation. Thin Solid Films 429, 201 (2003).CrossRefGoogle Scholar
4.Vella, J.B., Adhihetty, I.S., Junker, K. and Volinsky, A.A.: Mechanical properties and fracture toughness of organo-silicate glass (OSG) low-k dielectric thin films for microelectronic applications. Int. J. Fract. 119, 487 (2003).Google Scholar
5.Nix, W.D.: Mechanical properties of thin films. Metall. Trans. A 20, 2217 (1989).CrossRefGoogle Scholar
6.Vinci, R.P. and Vlassak, J.J.: Mechanical behavior of thin films. Annu. Rev. Mater. Sci. 26, 431 (1996).Google Scholar
7.Oliver, W.C. and Pharr, G.M.: Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology. J. Mater. Res. 19, 3 (2004).Google Scholar
8.Oliver, W.C. and Pharr, G.M.: An improved technique for determining hardness and elastic-modulus using load and displacement sensing indentation experiments. J. Mater. Res. 7, 1564 (1992).Google Scholar
9.Malzbender, J., Toonder, J.M.J. den, Balkenende, A.R. and de With, G.: Measuring mechanical properties of coatings: A methodology applied to nano-particle-filled sol-gel coatings on glass. Mater. Sci. Eng. R—Rep. 36, 47 (2002).CrossRefGoogle Scholar
10.Chen, X. and Vlassak, J.J.: Numerical study on the measurement of thin film mechanical properties by means of nanoindentation. J. Mater. Res. 16, 2974 (2001).Google Scholar
11.King, R.B.: Elastic analysis of some punch problems for a layered medium. Int. J. Solids Struct. 23, 1657 (1987).Google Scholar
12.Bhattacharya, A.K. and Nix, W.D.: Analysis of elastic and plastic-deformation associated with indentation testing of thin-films on substrates. Int. J. Solids Struct. 24, 1287 (1988).Google Scholar
13.Xiang, Y., Tsui, T.Y., Vlassak, J.J. and McKerrow, A.J.: Measuring the elastic modulus and ultimate strength of low-κ dielectric materials by means of the bulge test, in Proc. IEEE Int. Interconnect Tech. Conf., edited by IEEE (IEEE, Piscataway, NJ, 2004), p. 133.Google Scholar
14.Fleck, N.A., Otoyo, H. and Needleman, A.: Indentation on porous solids. Int. J. Solids Struct. 29, 1613 (1992).CrossRefGoogle Scholar
15.McElhaney, K.W., Vlassak, J.J. and Nix, W.D.: Determination of indenter tip geometry and indentation contact area for depth-sensing indentation experiments. J. Mater. Res. 13, 1300 (1998).Google Scholar
16.Tsui, T.Y., Vlassak, J.J. and Nix, W.D.: Indentation plastic displacement field: Part I. The case of soft films on hard substrates. J. Mater. Res. 14, 2196 (1999).Google Scholar
17.Tsui, T.Y., Vlassak, J.J. and Nix, W.D.: Indentation plastic displacement field: Part II. The case of hard films on soft substrates. J. Mater. Res. 14, 2204 (1999).Google Scholar
18.Saha, R. and Nix, W.D.: Effects of the substrate on the determination of thin film mechanical properties by nanoindentation. Acta Mater. 50, 23 (2002).Google Scholar
19.Bolshakov, A. and Pharr, G.M.: Influences of pileup on the measurement of mechanical properties by load and depth-sensing indentation techniques. J. Mater. Res. 13, 1049 (1998).Google Scholar
20.Chen, X., Xiang, Y. and Vlassak, J.J. A novel technique of measuring the mechanical properties of porous materials by nanoindentation: With application to low-k dielectric thin films. J. Mater. Res. (submitted) (2006).Google Scholar
21.Farnell, G.W. and Adler, E.L.: Physical Acoustics (Academic Press, New York and London, 1972).Google Scholar
22.Carlotti, G., Doucet, L. and Dupeux, M.: Comparative study of the elastic properties of silicate glass films grown by plasma enhanced chemical vapor. J. Vac. Sci. Technol. B 14, 3460 (1996).CrossRefGoogle Scholar
23.Huang, H.B. and Spaepen, F.: Tensile testing of free-standing Cu, Ag and Al thin films and Ag/Cu multilayers. Acta Mater. 48, 3261 (2000).Google Scholar
24.Read, D.T. and Dally, J.W.: A new method for measuring the strength and ductility of thin-films. J. Mater. Res. 8, 1542 (1993).CrossRefGoogle Scholar
25.Vlassak, J.J. and 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).Google Scholar
26.Xiang, Y., Chen, X. and Vlassak, J.J.: The plane-strain bulge test for thin films. J. Mater. Res. 20, 2360 (2005).Google Scholar
27.Martin, S.J., Godschalx, J.P., Mills, M.E., Shaffer, E.O. and Townsend, P.H.: Development of a low-dielectric constant polymer for the fabrication of integrated circuit interconnect. Adv. Mater. 12, 1769 (2000).Google Scholar
28.Zheng, D.W., Xu, Y.H., Tsai, Y.P., Tu, K.N., Patterson, P., Zhao, B., Liu, Q.Z. and Brongo, M.: Mechanical property measurement of thin polymeric-low-dielectric constant films using bulge testing method. Appl. Phys. Lett. 76, 2008 (2000).Google Scholar
29.Xiang, Y. and Vlassak, J.J.: Bauschinger effect in thin metal films. Scripta Mater. 53, 177 (2005).CrossRefGoogle Scholar
30.ASTM E92, Standard Test Method for Vickers Hardness of Metallic Materials (ASTM International, West Conshohocken, PA, 1987).Google Scholar
31.Tabor, D.: The Hardness of Metals (Clarendon Press, Oxford, U.K., 1951).Google Scholar
32.Lin, Y., Xiang, Y., Tsui, T.Y. and Vlassak, J.J. Octamethylcyclotetrasiloxane (OMCTS) based PECVD low-k organosilicate class (OSG) thin films. Part II: Mechanical properties and fracture (2005, unpublished).Google Scholar
33.Johnson, K.L.: Contact Mechanics (Cambridge University Press, Cambridge, MA, 1985).Google Scholar