Nanoindentation of Porous Materials: with Application to Low-k Dielectric Thin Films (Yong Xiang)

Many natural and engineered materials exhibit porous micro-structure, such as bones, thermal barrier coatings, and low-k dielectric thin films. Proper measurement of the mechanical properties of these porous materials is the first step toward analyzing and improving their mechanical reliability. A new technique for measuring the elastic-plastic properties of porous thin films by means of nanoindentation is proposed on the basis of finite element analysis. The technique is applied to low-k dielectric thin films that are used in the current and next generations of ultra-large-scale-integration circuits. After the substrate and densification effects in the nanoindentation have been properly corrected using the proposed models, the nanoindentation results agree well with the results from an independent measurement by bulge test.

 

Publications:

Y. Lin, T. Y. Tsui and J. J. Vlassak, "Octamethylcyclotetrasiloxane-based low-permittivity organosilicate coatings: composition, structure and polarizability", J. Electrochem. Soc. 153(7), F144-F152 (2006). (Download)

Y. Xiang, X. Chen, T. Y. Tsui, J.-I. Jang and J.J. Vlassak, "Mechanical properties of porous and fully dense low-k dielectric thin films measured by means of nanoindentation and the plane-strain bulge test technique", J. Mater. Res.21(2), 386-395 (2006). (Download)

X. Chen, Y. Xiang and J.J. Vlassak, "A novel technique of measuring the mechanical properties of porous materials by nanoindentation: with application to low-k dielectric thin films", J. Mater. Res. 21(3), 715-724 (2006). (Download)

Y. Xiang, T. Li, Z. Suo and J. J. Vlassak, "High ductility of a metal film adherent on a polymer substrate", Appl. Phys. Lett. 87, 161910 (2005). (Download)

Y. Xiang, T. Y. Tsui, J. J. Vlassak and A. J. McKerrow, "Measuring the elastic modulus and ultimate strength of low-k dielectric materials by means of the bulge test", Proceeding of the International Interconnect Technology Conference (IITC) IEEE, 133-135 (2004). (Download)

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Nanoindentation Analysis of Thin Films on a Substrate (Han Li)

A data analysis procedure has been developed to estimate the contact area in an elasto-plastic indentation of a thin film bonded to a substrate. The procedure can be used to derive the elastic modulus and hardness of the film from the indentation load, displacement, and contact stiffness data at indentation depths that are a significant fraction of the film thickness. The analysis is based on Yu’s elastic solution for the contact of a rigid conical punch on a layered half-space and uses an approach similar to the Oliver-Pharr method for bulk materials. The methodology is demonstrated for both compliant films on stiff substrates and the reverse combination and shows improved accuracy over previous methods.

Publications:
H. Li, N. X. Randall and J. J. Vlassak, "New methods of analyzing indentation experiments on very thin films", J. Mater. Res. 25(4), 728-734 (2010). (Download)

H. Li and J. J. Vlassak, "Determining the elastic modulus and hardness of an ultra-thin film on a substrate using nanoindentation", J. Mater. Res. 24(3), (2009). (Download)

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Problems in Anisotropic Contact Mechanics

Publications:

J. J. Vlassak, M. Ciavarella, J. R. Barber and X. Wang, "The indentation modulus of elastically anisotropic materials for indenters of arbitrary shape", J. Mech. Phys. Solids 51(9), 1701-1721 (2003). (Download)

J. J. Vlassak and W. D. Nix, "Measuring the elastic properties of anisotropic materials by means of indentation experiments", J. Mech. Phys. Solids 42(8), 1223-1245 (1994). (Download)

J. J. Vlassak and W. D. Nix, "Indentation modulus of elastically anisotropic half spaces", Philos. Mag. A 67(5), 1045-1056 (1993).