Twenty-first century opportunities for GSI will be governed in part by a hierarchy of physical limits on interconnects whose levels are codified as fundamental, material, device, circuit, and system. Fundamental limits are derived from the basic axioms of electromagnetic, communication, and thermodynamic theories, which immutably restrict interconnect performance, energy dissipation, and noise reduction. At the material level, the conductor resistivity increases substantially in sub-50-nm technology due to scattering mechanisms that are controlled by quantum mechanical phenomena and structural/morphological effects. At the device and circuit level, interconnect scaling significantly increases interconnect crosstalk and latency. Reverse scaling of global interconnects causes inductance to influence on-chip interconnect transients such that even with ideal return paths, mutual inductance increases crosstalk by up to 60% over that predicted by conventional RC models. At the system level, the number of metal levels explodes for highly connected 2-D logic megacells that double in size every two years such that by 2014 the number is significantly larger than ITRS projections. This result emphasizes that changes in design, technology, and architecture are needed to cope with the onslaught of wiring demands. One potential solution is 3-D integration of transistors, which is expected to significantly improve interconnect performance. Increasing the number of active layers, including the use of separate layers for repeaters, and optimizing the wiring network, yields an improvement in interconnect performance of up to 145% at the 50-nm node.

This article reports a novel hybrid multiscale carbon‐fiber/epoxy composite reinforced with self‐healing core‐shell nanofibers at interfaces. The ultrathin self‐healing fibers were fabricated by means of coelectrospinning, in which liquid dicyclopentadiene (DCPD) as the healing agent was enwrapped into polyacrylonitrile (PAN) to form core‐shell DCPD/PAN nanofibers. These core‐shell nanofibers were incorporated at interfaces of neighboring carbon‐fiber fabrics prior to resin infusion and formed into ultrathin self‐healing interlayers after resin infusion and curing. The core‐shell DCPD/PAN fibers are expected to function to self‐repair the interfacial damages in composite laminates, e.g., delamination. Wet layup, followed by vacuum‐assisted resin transfer molding (VARTM) technique, was used to process the proof‐of‐concept hybrid multiscale self‐healing composite. Three‐point bending test was utilized to evaluate the self‐healing effect of the core‐shell nanofibers on the flexural stiffness of the composite laminate after predamage failure. Experimental results indicate that the flexural stiffness of such novel self‐healing composite after predamage failure can be completely recovered by the self‐healing nanofiber interlayers. Scanning electron microscope (SEM) was utilized for fractographical analysis of the failed samples. SEM micrographs clearly evidenced the release of healing agent at laminate interfaces and the toughening and self‐healing mechanisms of the core‐shell nanofibers. This study expects a family of novel high‐strength, lightweight structural polymer composites with self‐healing function for potential use in aerospace and aeronautical structures, sports utilities, etc. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

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The development of polymers that can repair damage autonomously would be useful to improve the lifetime of polymeric materials. To date, limited attention has been dedicated to developing elastomers with autonomic self-healing ability, which can recover damages without need for an external or internal source of healing agents. This work investigates the self-healing behavior of epoxidized natural rubber (ENR) with two different epoxidation levels (25 and 50 mol % epoxidation) and of the corresponding unfunctionalized rubber, cis-1,4-polyisoprene (PISP). A self-adhesion assisted self-healing behavior was revealed by T-peel tests on slightly vulcanized rubbers. A higher epoxidation level was found to enhance self-healing. Self-healing of rubbers following ballistic damages was also investigated. A pressurized air flow test setup was used to evaluate the self-healing of ballistic damages in rubbers. Microscope (OM, SEM, and TEM) analyses were carried out to provide further evidence of healing in the impact zones. Self-healing of ballistic damages was observed only in ENR with 50 mol % epoxidation and it was found to be influenced significantly by the cross-link density. Finally, self-healing of ballistic damages was also observed in ENR50/PISP blends only when the content of the healing component (i.e., ENR50) was at least 25 wt %. From an analysis of the results, it was concluded that a synergistic effect between interdiffusion and interaction among polar groups leads to self-healing in ENR.

Silicon wafers, coated with 300 nm evaporated copper, were successfully bonded at 450°C for 30 min with a postbonding anneal in N 2 for 30 min. The postbonding anneal was required for successful bonding, but the annealing temperature did not influence the bond strength from 400 to 620°C. The inclusion of a tantalum diffusion barrier for Cu did not affect the bonding strength or the bonding temperature.Copper metallization, with low electrical resistivity and high electromigration resistance, 1 is rapidly developing into the mainstream interconnect technology. Along with advances in low k dielectrics, these are two practical approaches in reducing interconnect RC delay in integrated circuits. However, new schemes, such as direct three-dimensional integration, have shown promises in significant reduction of interconnect delay and an increase in system performance. 2,3 In exploring the implementation of 3-D integrated circuits, wafer bonding is an attractive technology option.In direct 3-D integration, active device wafers are bonded together, while all active layers are electrically interconnected using high aspect ratio vias. The bonded device wafers are assumed to contain multiple aluminum metal layers and interlevel dielectrics (ILD), thus requiring low-temperature bonding below 450°C to avoid Al degradation. 4 Referring to Fig. 1, one implementation of 3-D integration is to use polymer adhesives, such as polyimide or epoxy, to bond wafers at low curing temperatures ranging from 150 to 400°C. [5][6][7] Interwafer vias are then etched through the ILD, the thinned top Si wafer, and the cured polymer layer, with an approximate depth of 20 µm. 7 Furthermore, via filling is made using oxide spacers for insulation, chemical vapor deposited (CVD) TiN for the metal liner, and CVD W for plug formation.Instead of polymers, one can also use borophosphosilicate glass (BPSG) as the bonding adhesive. 8 However, when using low melting point glasses (450°C or more) for wafer bonding, global planarity of the glass film is needed for good contact between the wafers and to eliminate void formation. Thus, chemical mechanical polishing (CMP) or reflow of the glass is necessary prior to bonding. For both planarization methods, process variations are difficult to control. To alleviate processing issues such as film planarity or complex deeptrench etching procedures, a metal thermocompression bonding method has been proposed. Thin metal films from both wafers will fuse together upon applying compressive force and heat, which provide enough adhesion to bond the wafers together. 9 Figure 2 shows metal (Cu) bumps on both wafers that can serve as electrical contacts between via on the top wafer and Al interconnects on the bottom wafer. These metal bumps also function as small bond pads for wafer bonding. At the same time, dummy metal patterns can be made to increase the surface area for wafer bonding. They can also act as auxiliary structures such as ground planes or heat conduits for the Si active layers. This paper reports on Cu/Ta wafer...