Electromigration testing

Fig. 12 Last 30 m of the electromigration test on aluminium, please note that the measurement...

A drawback of this method is that micro-Raman spectroscopy cannot generally be applied to metallic materials. Furthermore, stress estimation can only be made on the basis of Raman spectra gathered in the substrate and the dielectric on the sides of the interconnect lines. Such measurements cannot be made in the region immediately below the line, where the stress is more uniform and more sensitive to the stress in the lines themselves, if the substrate is nontransparent. Despite these limitations, the micro-Raman spectroscopy method has been successfully used to infer the average values of internal stress components in interconnect lines tested in the as-fabricated condition as well as after electromigration testing (Ma et al. (1995) DeWolf et al. (1999)). 

Electromigration testing can be compromised by both overstressing and poor test structure design. To obtain test results in experimentally convenient time frames, accelerated testing must be performed. In these tests, stress conditions are chosen to be more severe than field conditions, and the test results are extrapolated ( decelerated ) to represent the expected performance in operation. Overstressing occurs when the test conditions are such that the results cannot be decelerated. This occurs if the choice of conditions excites failure modes that will not occur under normal operation. 

Examples of one-dimensional and two-dimensional models to predict the transport of heavy metals under constant DC current are explained in Chapter 25. This model ignores hydraulic advection, electrophoresis, diffusion, and electroosmosis processes and considers only electromigration. Electrical potential distribution is assumed to be a function of the electrical resistance of the soil and depends on the instantaneous local concentration and mobility of all the ions existing in the pore water of the soil. Local chemical equilibrium is assumed to calculate the concentration of chemical species. Validation of these and other developed models based on laboratory and field test results is critical to gain confidence in the accuracy of the model predictions. 

In the case of EDTA-enhanced test on prewashed sediment S (run EDTA-S), the results in terms of heavy metal mobilization were modest, with a slight accumulation of Cd and Pb in the central sections of the specimen, probably as a result of electromigration of negatively charged EDTA metal complexes toward the anode and an opposite mass transport caused by the electroosmotic flow toward the cathode (Fig. 7.10) however, the low metal mobilization may also derive from the lower voltage gradient applied (1 V/cm) if compared to tests on sediment V (2.5V/cm). 

On the other hand, tests with sodium dodecylbenzene sulfonate showed that PAH desorption could be accomplished by electromigration of anionic micelles in the direction of the anode the surfactant was injected at the cathodic side of the electrokinetic cell. PAH removal of 90% was seen in the cathodic region (Pamukcu, 1994). Consequently, it is apparent that anionic surfactants migrate against the electroosmotic flow, and hence, are less useful in EK than are nonionic surfactants, even though the anionic surfactants are less adsorbed onto soil than are nonionic materials. 

The literature comprises a larger number of methodologies employing electromigration principles, diverse preconcentration strategies, and a variety of detection schemes for pollutant standards combined as test mixtures and for real samples. Tables 31.1 through 31.9 compile representative applications of CZE and EKC methods to the most important classes of pollutants in different environmental compartments. 

The impact of different surfactants (SDS, DOSS, CTAB and hexadimethrine bromide, bile salts °), nonionic and mixed micelles, and additives (neutral and anionic CDs," " tetraalkylammonium salts, organic solvents in EKC separations has been demonstrated with phenol test mixtures. In addition, phenols have been chosen to introduce the applicability of more exotic EKC secondary phases such as SDS modified by bovine serum albumin, water-soluble calixarene, " starburstdendrimers, " " cationic replaceable polymeric phases, ionenes, amphiphilic block copolymers,polyelectrolye complexes,and liposome-coated capillaries. The separation of phenols of environmental interest as well as the sources and transformations of chlorophenols in the natural environment have been revised. Examples of the investigation of phenols by EKC methodologies in aquatic systems, soil," " and gas phase are compiled in Table 31.3. Figure 31.3 illustrates the electromigration separation of phenols by both CZE and EKC modes. 

Titanium Nitride (TiN) and Titanium (Ti) are the metals that are investigated as possible candidates for electrode arrays with Aluminium (Al) been used in our experiments for comparison purposes. Al which is being widely used in microelectronic industry as an interconnect, shows lower resistivity when combined with TiN. All of the measurements performed in the experimental setup are done on the same type of test die. There are four batches of this die, all of them are processed with different metals Al, TiN, Ti and one has aluminium covered with titanium nitride (Al-TiN). Following sections will provide you details about the experiments performed with the experimental setup on these materials and the results thereafter. Section 5.1 goes into detail about this test die. The test die was subjected to several tests and measurements the impedance of the different materials, the self-heating characteristics, the temperature coefficient of resistance (TCR), electromigration and endurance in a saline solution have all been measured out of which Electromigration, TCR and Impedance will be explained in detail in the later sections. 

Electromigration phenomenon is tested by driving current through the smallest (the 1 pm) track. The smallest track is chosen because of the high current density even though the heat dissipation stays low. This is relevant, because a failure due to a too... 

Many of the high-purity solvents now available for techniques including LC, electromigration and/or membrane separation, as well as for spectroscopy. However, purification and quality testing of even commercial products is often necessary before use, particularly in the above-mentioned techniques that are applicable to multicomponent systems. For... 

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