Effects of patterning on the interface toughness of wafer-level Cu–Cu bonds

Tadepalli, Rajappa; Turner, Kevin T.; Thompson, Carl V.

doi:10.1016/j.actamat.2007.10.016

Cited by 28 publications

(19 citation statements)

References 15 publications

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“…However, conventional J 2 -flow theory is applied here to reduce the difficulty of the numerical problem. An additional complication is that if interface debonding between the two Cu films occurs by atomistic separation in the experiments of Tadepalli et al (2008b), then one would expect d c n % 0:5 nm andr % 10 GPa consistent with a work of separation, C 0 $ 2 J m À2 . In the numerical implementation, values of d c n as small as 0.5 nm together with the much larger values of the Cu line dimensions D and H would require meshing refinements that are not computationally feasible.…”

Section: Problem Formulationmentioning

confidence: 82%

“…To relate the experimental results of Tadepalli et al (2008b) for orthogonal Cu lines to the present theoretical predictions their toughness measurements must be interpreted. Stable crack growth in the chevron specimens begins prior to attainment of a smooth peak load followed by a gradually decreasing load giving way to abrupt failure.…”

Section: Discussionmentioning

confidence: 98%

“…In the examples in Figs. 5 and 6 the length of the cohesive zone is a finite fraction of the line width, D, whereas in more realistic systems, such as those of Tadepalli et al (2008b), c is expected to be a tiny fraction of D, as discussed further below.…”

Section: Discussionmentioning

confidence: 98%

“…The work is motivated by the experimental studies of [Tadepalli, R., Turner, K.T., Thompson, C.V., 2008b. Effects of patterning on the interface toughness of wafer-level Cu-Cu bonds.…”

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confidence: 99%

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Analyses of crack growth along interface of patterned wafer-level Cu–Cu bonds

Tvergaard

Hutchinson

2009

International Journal of Solids and Structures

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a b s t r a c tA preliminary theoretical study is carried out of the role of micron-scale patterning on the interface toughness of bonded Cu-to-Cu nanometer-scale films. The work is motivated by the experimental studies of [Tadepalli, R., Turner, K.T., Thompson, C.V., 2008b. Effects of patterning on the interface toughness of wafer-level Cu-Cu bonds. Acta Materialia 56, 438-447; Tadepalli, R., Turner, K.T., Thompson, C.V., 2008c. Mixed-mode interface toughness of wafer-level Cu-Cu bonds using asymmetric chevron test. J. Mech. Phys. Solids 56, 707-718.] wherein 400 nm Cu films were deposited in a variety of patterns on Si wafer substrates. Specimens were then produced by bringing the Cu surfaces into contact creating thermocompression bonds. Interface toughness of these specimens was experimentally measured. The present study focuses on interface patterns comprised of bonded strips, called lines, alternating with lines of unbonded interface, all aligned parallel to the crack front. The interface toughness model employs a cohesive zone to represent separation of the interface and J 2 flow theory of plasticity to characterize the Cu films. Remote mode I loading is imposed on the elastic Si substrates. The computational model provides the resistance curve of macroscopic crack driving force versus crack advance as dependent on the work of separation and strength of the interface as well as the pattern geometry and the parameters controlling the plasticity of the Cu films. Plasticity in the Cu films makes a major contribution to the macroscopic interface toughness measured by Tadepalli, Turner and Thompson. Highlighted in this study is the difficulty of accurately representing plastic yielding in the thin films and the challenge of capturing the full range of scales in a computational model.

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Section: Problem Formulationmentioning

confidence: 82%

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 98%

“…The work is motivated by the experimental studies of [Tadepalli, R., Turner, K.T., Thompson, C.V., 2008b. Effects of patterning on the interface toughness of wafer-level Cu-Cu bonds.…”

mentioning

confidence: 99%

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Analyses of crack growth along interface of patterned wafer-level Cu–Cu bonds

Tvergaard

Hutchinson

2009

International Journal of Solids and Structures

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“…However, in their experiments the crack does not penetrate in the soft particles made of Nylon or polycarbonate leading to a process of crack trapping which can not be easily described in the framework of the crack pinning models. Recently, Tadepalli et al (Tadepalli et al, 2008) studied the effects of patterning on the interface toughness of Cu-Cu bonds. They show the influence of the orientation of the unidirectional patterns (lines) on the macroscopic toughness of their samples.…”

Section: Introductionmentioning

confidence: 99%

Crack front pinning by design in planar heterogeneous interfaces

Dalmas

Barthel

Vandembroucq

2009

Journal of the Mechanics and Physics of Solids

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The propagation of an interfacial crack front along the weak plane of a thin film stack is considered. A simple patterning technique is used to create a toughness contrast within this perfectly two-dimensional weak interface. The transparency of the specimens allows us to directly observe the propagation of the purely planar crack obtained during a DCB (Double Cleavage Beam) test. The effect on the crack front morphology of macroscopic unidimensional patterns in the direction of propagation is studied. In these weak pinning conditions, the geometry of the front quantitatively agrees with the first order expansion proposed by Gao and Rice (H. Gao and J.R. Rice, J.Appl. Mech., 56:828-838, 1989) which accounts for the effect of the interfacial crack front geometry on the stress intensity factor.

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