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Although the complex role of language in structuring experience and behavior is now widely recognized as a central element of historical understanding, the multiple problems of “representation” as they relate to late imperial and early Soviet politics remain a source of confusion and controversy. In particular, the role of nonworkers in organizing and leading “workers’ parties” has raised appropriate doubts about the very integrity of labor politics in these years, as well as the ways both Soviet and western historians have conceived them. Impressive new efforts have consequently been made, stimulated as well by advances in European labor history, to locate “authentic” worker voices and movements, and to contrast this socially grounded authenticity either directly or by implication with the abstracted idealizations of putative worker leaderships.
The development of electromigration-induced voids and hillocks in Al - 4 wt. % Cu interconnects is monitored by scanning electron microscopy during interrupted testing and is correlated directly with the actual grain configuration including precipitates. The short segments under study and their grain structures are defined and observed using focused ion beam microscopy. The Cu content in precipitate grains is swept away before electromigration damage, and at most such grains there is subsequent grain thinning. The observations are compared with the results from a computer simulation based on a finite-element calculation of self-consistent current density and temperature distributions. For the first time the simulation uses the actual grain configuration and incorporates Cu atom migration, and back-fluxes driven by stress and concentration gradients. In the simulation the grain-boundary diffusivity is taken to be independent of boundary misorientation or is varied according to randomly assigned orientations. The comparison of the voiding in these two simulated cases and the observations shows that some grain configurations are very susceptible to electromigration damage whatever the diffusivities. For most configurations, however, the misorientation dependence of grainboundary diffusivity is significant and must be included if simulations are to be realistic.
We have observed fluctuations in the tunneling current through 3.5 nm gate oxides with a 1/f power spectrum where f is the frequency. For voltages in the direct tunneling regime we lind an anomalous current dependence of the noise relative to previous observations of noise in thin oxides. We present a simplified model for the current noise in terms of fluctuations in a trap assisted tunneling current that exists in the oxide in addition to the direct tunneling current. Current noise appears to be a very sensitive probe of trap assisted tunneling and degradation in oxides.
Patterned 930 nm Al(1%-Si) interconnects over 147 nm of Cu were electromigration lifetime tested at 1.0–1.5 × 105 A/cm2 at 250 °C. The morphology of the surfaces of the electromigrated stripes with different line widths and times to failure were characterized by atomic force microscopy, and changes in surface roughness were compared. The diffusion of copper into the electromigrated aluminum stripes was determined by depth profiling using Auger electron spectroscopy. In particular, areas where hillocks formed were examined and compared to areas of median roughness.
Residual strains in thin films of 1.0 μm, 0.5 μm and 0.25 μm Cu capped with 24 nm Ta and a 62 nm Ta diffusion barrier were measured using x-rays during continuous temperature ramping. Cycles up to 300°C and 400°C were performed. At ambient temperature, the flow stresses after heating to 400°C were found to increase wth decreasing film thickness. The stresses were sufficiently high below 100°C to cause plastic yielding. The diffracted intensities from the in-plane and out-of-plane (111) planes were recorded with temperature and the intensity changes were attributed to the necessary dislocation density and distribution variation to accomodate the mismatch strain due to thermal expansion differences.
Mechanical stress and its relaxation in aluminum metallization in integrated circuits (IC) are a major concern for the reliability of the material. It is known that adding Cu improves the reliability but complicates plasma etching and increases corrosion sensitivity. The mechanical behavior of AIVPd, AlCu and Al blanket films is investigated by wafer curvature measurements. During thermal cycling between 50°C and 400°C the highest tensile stress is found in AIVPd. In a subsequent experiment, the cooling was interrupted at several temperatures to investigate the stress behavior during an eight hour isothermal treatment. Isothermal stress relaxation has been observed in the three types of films and is discussed.