Evaluation of the Dominant Factor for Electromigration in Sputtered High Purity Al Films

This paper is focused on evaluating the dominant factor for electromigration (EM) in sputtered high purity Al films. A closed-form equation of atomic flux divergence by treating grain boundary diffusion and hillock formation in a polycrystalline structure without passivation layer was derived to construct the theoretical model. According to the developed equation, it is available to see the effect of various parameters on the EM resistance. Moreover, based on the proposed model, we compared the EM resistance of different sputtered high purity Al films. These films differ in purity and features, which are realized as affecting factors for the EM resistance. Finally, according to the analysis by the synthesis of the obtained EM resistance, the evaluation of the dominant factor for EM in sputtered high purity Al films was approached. Although the effects of the average grain size and the effective valence cannot be ignored, the difference in diffusion coefficient was believed to have a dominant influence in determining the EM resistance. Thus, increasing the activation energy for grain boundary diffusion can significantly reduce the damage during EM in such sputtered polycrystalline Al films.

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Grain Boundary Diffusion and Segregation in the Solid State Phase Transformations

MRS Proceedings ◽

10.1557/proc-527-255 ◽

1998 ◽

Vol 527 ◽

Author(s):

E. Rabkin ◽

W. Gust

Keyword(s):

Grain Boundary ◽

Grain Boundaries ◽

Boundary Diffusion ◽

Grain Boundary Diffusion ◽

Solute Diffusion ◽

Apparent Difference ◽

Impurity Drag ◽

The Difference ◽

Boundary Width ◽

Dynamic Segregation

ABSTRACTWe consider the problem of solute diffusion and segregation in the grain boundaries moving during a phase transformation in the framework of Cahn's impurity drag model. The concept of a dynamic segregation factor for the diffusion along moving grain boundaries is introduced. The difference between static and dynamic segregation factors may cause the apparent difference of the triple product of the segregation factor, grain boundary width and grain boundary diffusion coefficient for stationary and moving grain boundaries. The difference between static and dynamic segregation is experimentally verified for the Cu(In)-Bi system, for which the parameters of static segregation are well-known. It is shown that the complications associated with the dynamic segregation may be avoided during the study of the discontinuous ordering reaction. From the kinetics of this reaction, the activation energy of the grain boundary self-diffusion can be determined.

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Grain boundary diffusion of 59Fe in high-purity copper

Acta Materialia ◽

10.1016/j.actamat.2018.11.060 ◽

2019 ◽

Vol 165 ◽

pp. 431-443 ◽

Cited By ~ 1

Author(s):

Jens Ribbe ◽

Vladimir A. Esin ◽

Sergiy V. Divinski

Keyword(s):

Grain Boundary ◽

High Purity ◽

Boundary Diffusion ◽

Grain Boundary Diffusion ◽

Purity Copper

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Grain Boundary Diffusion of Hydrogen in Nano-Structured Pd/Ag Alloy Membranes

ASME 2008 3rd Energy Nanotechnology International Conference ◽

10.1115/enic2008-53014 ◽

2008 ◽

Author(s):

Logan S. McLeod ◽

Levent F. Degertekin ◽

Andrei G. Fedorov

Keyword(s):

Grain Boundary ◽

Diffusion Process ◽

Grain Boundaries ◽

Boundary Diffusion ◽

Grain Boundary Diffusion ◽

Coarse Grained ◽

Appreciable Amount ◽

Bottom Surface ◽

Fast Diffusion ◽

Average Grain Size

Palladium and its alloys have long been used as hydrogen separation membranes due to their extremely high permeability and selectivity to hydrogen over all other gases [1]. The hydrogen permeation process begins with selective chemisorption of the gas onto the metal surface. As the adsorption process is the point in the permeation sequence where the majority of gases become excluded, it follows that a cleverly designed device could be created to take advantage of the so-called ‘fast’ diffusion paths of surface and grain-boundary diffusion to further enhance permeability without sacrificing selectivity. The contribution of grain-boundary diffusion to the overall permeation rate is dependent on the relative volume in the membrane occupied by grain-boundaries versus bulk material. Typically, grain boundaries only make up a miniscule fraction of the overall volume and therefore only contribute an appreciable amount to the overall diffusion process at temperatures low enough to make the bulk diffusion process nearly stagnant. However, in the case of a nanostructured membrane this paradigm is no longer valid. The fabrication methods associated with extremely thin membrane deposition typically lead to highly non-equilibrium microstructure with an average grain size on the order of tens of nanometers [2]. In order to exploit the potential advantages of grain boundary diffusion the nano-scale grains must persist throughout operation. To avoid the tendency for the grain structure to relax to a more equiaxed, coarse-grained morphology the self-diffusion of metal atoms in the film must be minimized by operating the membranes at a temperature much lower than the membrane melting temperature. Figure 1 shows the microstructural changes in a thin, sputtered, Pd/Ag alloy film before and after annealing. The initial fine-grained structure on the bottom surface of the membrane is due to a combination of low substrate temperature during deposition and the Ti adhesion layer onto which the Pd/Ag layer was deposited. After annealing at 400 C the grains have coarsened and the top and bottom structure are identical.

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Simulation of Hot Sheet Metal Forming Processes Based on a Micro-Structural Constitutive Model

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.473.556 ◽

2011 ◽

Vol 473 ◽

pp. 556-563 ◽

Cited By ~ 3

Author(s):

Mahmoud Farzin ◽

Reza Jafari Nedoushan ◽

Mohammad Mashayekhi

Keyword(s):

Experimental Data ◽

Grain Boundary ◽

Constitutive Model ◽

Strain Rate ◽

Boundary Diffusion ◽

Grain Boundary Sliding ◽

Grain Boundary Diffusion ◽

Hot Forming ◽

Proposed Model ◽

Boundary Sliding

A constitutive model is proposed for simulations of hot forming processes. Dominant mechanisms in hot forming including inter-granular deformation, grain boundary sliding and grain boundary diffusion are considered in the constitutive model. A Taylor type polycrystalline model is used to predict inter-granular deformation. Previous works on grain boundary sliding and grain boundary diffusion are extended to drive three dimensional macro stress-strain rate relationships for each mechanism. In these relationships, the effect of grain size is also taken into account. It is shown that for grain boundary diffusion, stress-strain rate relationship obeys the Prandtl-Reuss flow rule. The proposed model is used to simulate step strain rate tests and the results are compared with experimental data. It is concluded that the model can be used to predict flow stress for various grain sizes and strain rates. The proposed model can be directly used in simulation of hot forming processes and as an example the bulge forming process is simulated and the results are compared with experimental data.

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