Electromigration-induced plasticity and texture in Cu interconnects

Plastic deformation has been observed in damascene Cu interconnect test structures during an in-situ electromigration experiment and before the onset of visible microstructural damage (ie. voiding) using a synchrotron technique of white beam X-ray microdiffraction. We show here that the extent of this electromigration-induced plasticity is dependent on the texture of the Cu grains in the line. In lines with strong <111> textures, the extent of plastic deformation is found to be relatively large compared to our plasticity results in the previous study [1] using another set of Cu lines with weaker textures. This is consistent with our earlier observation that the occurrence of plastic deformation in a given grain can be strongly correlated with the availability of a <112> direction of the crystal in the proximity of the direction of the electron flow in the line (within an angle of 10{sup o}). In <111> out-of-plane oriented grains in a damascene interconnect scheme, the crystal plane facing the sidewall tends to be a {l_brace}110{r_brace} plane,[2-4] so as to minimize interfacial energy. Therefore, it is deterministic rather than probabilistic that the <111> grains will have a <112> direction nearly parallel to the direction of electron flow. Thus, strong <111> textures lead to more plasticity, as we observe

Alarm vigilance in the presence of 80 dBA pink noise with negative signal-to-noise ratios

Workers often have to be vigilant for critical auditory signals in the presence of loud noise. However this phenomenon appears to have received relatively less attention especially when the signal-to-noise ratios (SNRs) are less than unity (or - ve dB). In this study we focus on alarm vigilance in the presence of loud pink noise (80 dBA) and with SNR of -18, -21, -24 and -∞dB. The results show that people with no known hearing impairments, were able to detect a 56 dBA alarm in the presence of a noise level of 80 dBA (i.e., a SNR of -24 dB). The findings can help to establish threshold boundaries for audible alarm signal in the presence of loud noise

Effects of Presentation Method & Duration on Alarm Detection Threshold in the Presence of Loud Pink Noise

Detection of pure tone signals in the presence of noise has been thoroughly studied. Most of these studies have used monaural presentation of audio stimuli. Also, studies testing alarm detection in the presence of noise are limited. In 2013, Karunarathne et al., conducted a study and found out that human listeners were able to detect an alarm in negative signal-to-noise ratios (SNRs), as low as −24 dB. This study aims to investigate the effects of presentation method and duration of the alarms on detection threshold. Eight conditions varied by presentation method (monaural vs spatial) and alarm duration were tested. Sixteen human subjects with normal hearing were given the task of identifying which one of two sound intervals contained an alarm along with 80dBA pink noise. Thresholds were estimated as the 79.4% points on the psychometric functions, using adaptive 2-Interval Forced Choice (2IFC) procedure with a 3-down 1-up rule. Results indicated that detection thresholds were statistically significantly lower in spatial condition compared to monaural. The effect of alarm duration was not significant in both spatial and monaural conditions. Thresholds lower than −30 dB SNR were observed in the spatial condition, which agreed with the findings of Karunarathne et al. and further extended threshold boundaries

Electromigration-induced Plasticity: Texture Correlation and Implications for Reliability Assessment

Plastic behavior has previously been observed in metallic interconnects undergoing high current density electromigration (EM) loading. In this study of Cu interconnects, using the synchrotron technique of white beam X-ray microdiffraction, we have further found preliminary evidence of a texture correlation. In lines with strong (111) textures, the extent of plastic deformation is found to be relatively large compared to that of weaker textures. We suggest that this strong (111) texture may lead to an extra path of mass transport in addition to the dominant interface diffusion in Cu EM. When this extra mass transport begins to affect the overall transport process, then the effective diffusivity, D{sub eff}, of the EM process is expected to deviate from that of interface diffusion only. This would have fundamental implications. We have some preliminary observations that this might be the case, and we report its implications for EM lifetime assessment in this manuscript

Plasticity-amplified diffusivity: dislocation cores as fast diffusion paths in Cu interconnects

The mass transport of Cu during electromigration (EM) testing is typically dominated by interface diffusion. If a mechanism other than interface diffusion begins to affect the overall transport process, then the effective diffusivity, D, of the EM process would deviate from that of interface diffusion only. This would have fundamental implications. We have preliminary evidence that this might be the case, and we report its implications for EM lifetime assessment in this manuscript. (11 References)

Developmental stage-specific contribution of LGR5(+) cells to basal and luminal epithelial lineages in the postnatal mammary gland

The leucine-rich repeat-containing heterotrimeric guanine nucleotide-binding protein-coupled receptor 5 (LGR5) has been identified as a marker of cycling stem cells in several epithelial tissues, including small intestine, colon, stomach and hair follicle. To investigate whether LGR5 also marks mammary epithelial stem cells, we performed in situ lineage-tracing studies and mammary gland reconstitutions with LGR5-expressing mammary epithelial cells. Interestingly, the LGR5 progeny population in mammary epithelium switches from the luminal to the myoepithelial compartment during the first 12 days of postnatal development, likely reflecting local changes in Wnt signalling. Together, our findings point to a stage-specific contribution of LGR5-expressing cells to luminal and basal epithelial lineages during postnatal mammary gland development