Papers by Keyword: Electromigration

Abstract: The driving force on an ion in a metal due to an applied electric field, called the electromigration force, is built up out of two contributions, a wind force and a direct force. The wind force is due to the scattering of the current carrying electrons off the ion. The direct force works on the effective charge of the ion. In the present work we concentrate on the direct force on a migrating proton embedded in an electron gas. For this force a sign change is obtained as soon as a bound state is formed. In recent calculations hardly a sign change was seen, although a bound state was found in a self-consistent-potential for lower electron densities. Here we show that a supplementary term shows up, as soon as one accounts for the bound state explicitly. By this the problem has been solved regarding a possible lack of completeness of the published formalism. The results presented are based on square-well model potentials. By using different depths it is possible to show results for potentials without a bound state and accommodating one bound state.

Abstract: Based on measuring inhibitor effective component N content, chloride removal efficiency and steel polarization resistance, influences of technical parameters of concrete and electric charge amount on the inhibitor electromigration anticorrosion efficiency were described. The results indicated that inhibitor electromigration anticorrosion technology could remove chloride ion, and inhibitor group could move to steel surface so rapidly that corrosive steel could return into passive state, to meet the anticorrosion aim for steel.

Abstract: Migration of atoms is presented to be utilized for fabrication of metallic micro/nanomaterials by controlling the phenomenon. Two kinds of migration phenomena are treated; one is electromigration and the other is stress migration. In addition to the formation of micro/nanomaterials, some achievements in enhancing their functions are demonstrated. One is a technique to fabricate nanocoils from the formed Cu nanowires. The others are techniques to weld or cut the micro/nanowires by using Joule heating. Finally, regarding evaluation of mechanical and electrical properties of the micro/nanomaterials, the concentrated-mass cantilever technique in atomic force acoustic microscopy and the four-point atomic force microscope technique are shown to be powerful tools, respectively.

Abstract: Metallic interconnection electromigration is a common phenomenon in integral circuit, and it influences circuit reliability seriously as rapid miniaturization of circuit size. Resistance is a traditional electromigration characterization parameter, but it requires strict testing condition, and it is not sensitive to vacancies accumulation at early stage of electromigration. Some recent researches show that noise is very sensitive to metallic thin film electromigration, it can be used as an effective inspect method for electromigration. So noise wais used to characterize damage degree of Al thin film electromigration in this paper., Tthe results showeds both noise amplitude and frequency exponent increased during electromigration process, and when void nucleation occuredhappens, frequency exponent increased sharply. noise can also reflect electromigration degree under different environment temperature. Through comparing with resistance, noise can be proved a better characterization parameter for electromigration

Abstract: In advanced electronic products, electromigration-induced failure is one of the most serious problems in fine pitch flip chip solder joints because the design rule in devices requires high current density through small solder joints for high performance and miniaturization. The failure mode induced by electromigration in the flip chip solder joint is unique, owing to the loss of under bump metallurgy (UBM) and the interfacial void formation at the cathode contact interface. In this study, Electromigration of flip chip solder joints has been investigated under a constant density of 2.45×104 A/cm2 at 120 °C. The in-situ marker displacements during the electromigration test was measured and found to show a rough linear change as a function of time. Scanning electron microscopic images of the cross section of samples showed the existence of voids at the interface between Al interconnection and under bump metallurgy. The void movement was matched with the marker displacements during the electromigration test, and voids moved to the cathode interface between Al interconnection and under bump metallurgy in the downward electron flow (from chip to substrate) joint. The mechanism of electromigration-induced void migration and failure in the flip chip are discussed. During electromigration, a flux of atoms is driven from the cathode to the anode or a flux of vacancies in the opposite direction. It can lead to two possible mechanisms of void migration. First, if we regard the void as a rigid marker of diffusion, it will be displaced towards the cathode by the atomic flux in the electromigration, Second, if we consider surface diffusion on the void surface, electromigration will drive atoms on the top surface of the void to the bottom surface of the void, and consequently the void will move towards the cathode.

Abstract: The morphological evolution of intragranular voids induced by the surface drift-diffusion under the action of capillary forces, electromigration (EM) forces, and thermal stress gradients (TSG) associated with steady state heat flow is investigated in passivated metallic thin films via computer simulation using the front-tracking method. As far as the device reliability is concerned, the most critical configuration for interconnect failure occurs even when thermal stresses are low if the normalized ratio of interconnect width to void radius is less than certain range of values (which indicates the onset of heat flux crowding). This regime manifests itself by the formation of two symmetrically disposed finger shape extrusions (pitchfork shape slits) on the upper and lower shoulders of the void surface on the windward side. The void growth (associated with supersaturated vacancy condensation) on the other hand inhibits anode displacement but enhances cathode and shoulder slit velocities drastically, which causes lateral spreading.

Abstract: Spark-Plasma Sintering (SPS) involves rapid heating of powder by electric current with simultaneous application of external pressure. Numerous experimental investigations point to the ability of SPS to render highly-dense powder products with the potential of grain size retention. The latter ability is of significance for the consolidation of nano-powder materials where the grain growth is one of the major problems. A model for spark-plasma sintering taking into consideration various mechanisms of material transport is developed. The results of modeling agree satisfactorily with the experimental data in terms of SPS shrinkage kinetics.

Abstract: As silicon ICs continue to scale down, several reliability issues have emerged. Electromigration- the transportation of metallic atoms by the electron wind- has been recognized as one of the key damage mechanisms in metallic interconnects. It is known that there is a threshold current density of electromigration damage in via-connected lines. The evaluation of the threshold current density is a matter of the great interest from the viewpoint of IC reliability. In this study, Al polycrystalline lines with two-dimensional shape, i.e. angled lines are experimentally treated for the evaluation. Comparing the experimental result with that of straight-shaped line, the effect of line-shape on the threshold current density of electromigration damage is discussed.

Abstract: In-situ observation by scanning electron microscope of the microstructure evolution near the cathode depletion region and the quantitative analysis on the number of hillock phases in the eutectic SnPb edge drift structure made it clear that the dominant migrating element and dominant hillock phase were Sn and Pb, respectively, under 50 oC while both dominant migrating element and dominant hillock phase were Pb above 100 oC. Such temperature-dependence of the dominant hillock phases in the eutectic SnPb solder can be understood by considering the atomic size factors of the metallic solid solutions.