Secondary electron imaging of embedded defects in carbon nanofiber via interconnects

Carbon nanofiber (CNF) via interconnect test structures are fabricated with the bottom-up process proposed by Li et al. [Appl. Phys. Lett. 82, 2491 (2003)] for next-generation integrated circuit technology. Critical defects in the interconnect structure are examined using scanning electron microscopy. It is shown that secondary electron signal with optimized incident beam energy is useful for detecting embedded defects, including unexposed CNF plugs and voids in the dielectric layer. The defect imaging mechanisms are elucidated based on beam-induced charging of the specimen surface

Bright-field transmission imaging of carbon nanofibers on bulk substrate using conventional scanning electron microscopy

The authors present scanning transmission electron microscopy (STEM) of carbon nanofibers (CNFs) on a bulk substrate using conventional scanning electron microscopy (SEM) without specimen thinning. By utilizing the electron beam tilted \u3e85° from the substrate normal, bright-field STEM contrast is obtained for the CNFs on substrate with conventional SEM. Analysis of the observed contrast using Monte Carlo simulation shows that the weakly scattered electrons transmitted from the CNF are selectively enhanced by the largely tilted substrate and result in the observed STEM contrast. This mechanism provides a useful STEM imaging technique to investigate the internal structure of materials on bulk substrates without destructive specimen thinning

Structural Characteristics of Carbon Nanofibers for On-chip Interconnect Applications

In this letter, we compare the structures of plasma-enhanced chemical vapor deposition of Ni-catalyzed and Pd-catalyzed carbon nanofibers (CNFs) synthesized for on-chip interconnect applications with scanning transmission electron microscopy (STEM). The Ni-catalyzed CNF has a conventional fiberlike structure and many graphitic layers that are almost parallel to the substrate at the CNF base. In contrast, the Pd-catalyzed CNF has a multiwall nanotubelike structure on the sidewall spanning the entire CNF. The microstructure observed in the Pd-catalyzed fibers at the CNF-metal interface has the potential to lower contact resistance significantly, as our electrical measurements using current-sensing atomic force microscopy indicate. A structural model is presented based on STEM image analysis

Current-induced breakdown of carbon nanofibers

We present a study of high-field transport in carbon nanofibers (CNFs) and breakdown phenomena due to current stress. In situ measurements with scanning transmission electron microscopy reveal that the failure mode of CNFs is strongly related to the morphology of graphite layers comprising CNFs. Comparison with carbon nanotube (CNT) breakdown is made, demonstrating that the current capacity of CNFs is described by a similar model as that of CNTs with a modification of the current capacity of each graphitic layer. The maximum current density is correlated with resistivity, leading to the conclusion that lower resistivity results in higher current capacity in CNFs

Interface Characteristics of Vertically Aligned Carbon Nanofibers for Interconnect Applications

The authors characterize the detailed interface structure of Ni-catalyzed vertically aligned carbon nanofibers (CNFs) prepared by plasma-enhanced chemical vapor deposition for interconnect applications. Stacked graphitic layers and cup-shape structures of CNFs around the interface region have been observed using high-resolution scanning transmission electron microscopy. The interaction between the Ni catalyst and Ti layer dramatically affects the CNF structure during initial growth. The effect of interface nanostructures on contact resistance is also discussed

Growth of Carbon Nanofibers on Nanoscale Catalyst Strips Fabricated with a Focused Ion Beam

We studied the growth mode of vertically aligned carbon nanofibers (CNFs) on Ni catalyst strips fabricated using a focused ion beam (FIB). We found that the CNF growth on Ni catalysts was strongly affected by the geometry of the microfabricated Ni catalyst strips. Selective growth of vertically aligned CNFs requires ion milling from the outside edge of the sample so that the milled materials are effectively evacuated. The CNF diameter and density on the strip depends on its width. Possible mechanisms to control CNF growth using microfabricated catalysts are analyzed with a liquid model using surface free energies

High-throughput isolation of giant viruses using high-content screening

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