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Antireflection (AR) films are useful for preventing the reflection of light from flat-panel displays, solar-cell panels, optical lenses, and similar structures. We previously reported the successful high-throughput fabrication of an AR structure (ARS) with less than 0.1% reflectivity by means of ultraviolet nanoimprint lithography (UV-NIL). However, this process tended to produce a thick residual layer that reduced transmittance and produced interfacial reflections at surfaces of lenses coated with the ARS. To reduce interfacial reflections, the thickness of the residual layer must be less than 100nm or so (roughly a quarter of the wavelength of visible light). Liquid transfer imprint lithography (LTIL) is an effective technique for reducing the thickness of the residual layer. In the LTIL process, residual resin is eliminated by separating the mold and substrate in the liquid phase. This process is also effective for curved surfaces, and it has been reported an ARS with a thin residual layer can be obtained by LTIL. However, the method that was used required a vacuum process and was time consuming. To obtain a thin residual layer at atmospheric pressure, we devised an LTIL process involving a roll-press method that does not require the presence of a vacuum. The technique permitted the fabrication of a high-performance ARS with improved reflectance and transmittance thickness, in which the thickness of the residual layer was less than a quarter of the wavelength of visible light. Furthermore, the technique could be used to produce a homogeneous ARS with a residual layer less than 100nm thick on a curved surface, such as that of a lens, in a reproducible and stable manner. The process is therefore suitable for fabricating ARSs that show a high performance with a thin residual layer on curved surfaces such as convex lenses. Display Omitted We devised an LTIL with roll-press method that does not require a vacuum process.An ARS with a residual layer less than 100-nm thick was homogeneously formed over the curved surface.The reflectance and transmittance was improved by fabricating an ARS at lens surface.

The mechanism of dense vertically aligned carbon nanotube growth achieved by a recently developed thermal chemical vapor deposition method was studied using synchrotron radiation spectroscopic techniques., The mechanism of the one-order-of-magnitude increase in the density of vertically aligned carbon nanotubes (CNTs) achieved by a recently developed thermal chemical vapor deposition process was studied using synchrotron radiation spectroscopic techniques. In the developed process, a Ti film is used as the underlayer for an Fe catalyst film. A characteristic point of this process is that C2H2 feeding for the catalyst starts at a low temperature of 450°C, whereas conventional feeding temperatures are ∼800°C. Photoemission spectroscopy using soft and hard X-rays revealed that the Ti underlayer reduced the initially oxidized Fe layer at 450°C. A photoemission intensity analysis also suggested that the oxidized Ti layer at 450°C behaved as a support for nanoparticle formation of the reduced Fe, which is required for dense CNT growth. In fact, a CNT growth experiment, where the catalyst chemical state was monitored in situ by X-ray absorption spectroscopy, showed that the reduced Fe yielded a CNT forest at 450°C. Contrarily, an Fe layer without the Ti underlayer did not yield such a CNT forest at 450°C. Photoemission electron microscopy showed that catalyst annealing at the conventional feeding temperature of 800°C caused excess catalyst agglomeration, which should lead to sparse CNTs. In conclusion, in the developed growth process, the low-temperature catalyst activation by the Ti underlayer before the excess Fe agglomeration realised the CNT densification.

Carbon-based materials, such as carbon nanotubes and graphene nanoribbons, have been studied as interconnect materials because of their lower resistivity, higher thermal conductivity, and intrinsically higher current carrying capacity compared to Cu. We have succeeded in growing networked-nanographite (NNG) films on dielectric layers without any metal catalysts, and fabricated NNG wires as the first step toward multi-layer graphene interconnects. In this study, we investigated the electrical properties and reliability, such as current tolerance and thermal stability, of these NNG wires. In addition, we investigated the mechanism of resistivity decreases in NNG. Our results show that the NNG wires can sustain a higher current density than Cu wires. However, their resistivity gradually decreases due to thermal stress. Raman and X-ray photoelectron spectroscopy revealed that the decrease in resistivity can be attributed to an increase in sp2 bonding corresponding to the formation of a graphene sheet. It is important to clarify the mechanism of the decrease in resistivity, not only to improve thermal stability but also to obtain lower resistivity in carbon interconnects.

Selective synthesis of carbon nanotubes (CNTs) and graphene was achieved by hot-filament chemical vapor deposition (CVD) using iron films as a catalyst at a temperature of 620 °C. The selective synthesis was performed in a very simple way, just by changing the catalyst thickness under the same CVD conditions. Only CNTs were obtained with Fe films of 5 nm and less, while multi-layer graphene was formed with the catalyst films of 20 nm and more. The thickness of multi-layer graphene can also be controlled by controlling the thickness of the catalyst further.

We are trying to employ nano-carbon materials, such as graphene and carbon nanotubes (CNTs), as channel and interconnect materials to realize low-power-consumption large-scale integrated circuits (LSIs). In this paper, we first explain our recent progress on the application of graphene to transistor channels. Graphene synthesis on a 200-mm Si wafer by chemical vapor deposition (CVD) and electrical properties of CVD-graphene transistors are described. Especially, details of graphene growth on Cu film, such as nucleation behavior of graphene islands depending on the growth condition, are addressed. Efforts to realize CNT interconnects at MIRAI-Selete are also reviewed. Special emphases are placed on the fabrication process of CNT vertical interconnects and their reliability.

Multiwalled carbon nanotubes (MWCNTs) were synthesized at 390 °C in a hydrogen-free atmosphere by graphite antenna chemical vapor deposition, which provides carbon radicals by the etching of the antenna itself in a He- or Ar-based noble gas plasma. An increase in the number of defects in the graphite layers of the CNTs was observed with increasing hydrogen partial pressure. The results of X-ray photoelectron spectroscopy analysis suggested that these defects were caused by the transformation from an sp 2 to an sp 3 structure in the graphite layers of CNTs due to hydrogen radicals.

In order to grow multi-layer graphene for LSI interconnection at the low temperature without any catalyst, the growth temperature dependence of multi-layer graphene formed by photoelectron-assisted plasma chemical vapor deposition is investigated using microscopic Raman spectroscopy and bulk-sensitive X-ray photoelectron spectroscopy. The samples were grown at the temperatures from room temperature (RT) to 700oC by using an Ar/CH4 gas mixture on a Si(001) substrate with native oxide. At temperatures as high as 700oC, shiny black films are obtained, suggesting the growth of graphite. From G band position and FWHM in Raman spectra, it is found that the abundance of graphene sheet is considerably reduced when the growth temperature is lowered below 500oC, leading to an increase of amorphous. This tendency is in accordance with the temperature dependence of the ratio between amorphous graphene components in C 1s spectra.

We have developed a photoemission-assisted plasma-enhanced chemical vapor deposition (CVD) process, where DC discharge plasma is assisted by photoelectrons emitted from the substrate under ultraviolet (UV) light irradiation. Under Ar gas atmosphere and in vacuum, plasma current was measured as a function of sample bias voltage to clarify the mechanism, by which photoemission-assisted plasma is generated. Owing to the advantages of the photoemission-assisted plasma-enhanced CVD, where the plasma is generated close to the substrate and in a controllable volume, we have succeeded in growing shiny black films of networked nanographite, without any catalyst, on Si(001) and SiO2(350 nm)/Si(001) substrates at a deposition rate of ∼2 μm/min despite of low electric power consumption of plasma, ∼4 W. Cross-sectional transmission electron microscopy (TEM) and diffraction (TED) observations revealed that samples grown at ∼700°C with Ar-diluted CH4 were composed of multilayer graphene particles (diameter of ∼10 nm) that were closely connected to each other and shared some graphene sheets between them, although their crystallographic configurations were randomly oriented. In bulk-sensitive C 1s photoelectron spectra using synchrotron radiation at 7933 eV, a chemically-shifted component of sp2-bonded carbon atom was dominant and the π—π* transition loss peak was clearly observed for the samples grown on both substrates, indicating that the multilayer graphene particles substantially contain high-quality graphene sheets in agreement with evaluations by microscopic Raman spectroscopy. We named the layered carbon structure “carbon mille-feuille.” [DOI: 10.1380/ejssnt.2009.882]

Thermal conductivity of a multi-walled carbon nanotube (MWNT) was evaluated using the ΔVgs method for the first time. MWNTs were prepared in pillars, and the pillars were placed on two aluminum nitride (AlN) substrates. An AlGaN/GaN high electron mobility transistor (HEMT) chip, which was set on an AlN substrate, was used as a thermometer and as a thermal source. The thermal resistance of the sample was measured using the ΔVgs method. From the thermal resistance of MWNT pillars, we succeeded in evaluating the thermal conductivity of a MWNT pillar and that of a MWNT as high as 74.2 and 950 W/(mK), respectively. The thermal conductivity of MWNTs evaluated in this study is much higher than that of usual metals. We confirmed that MWNTs are promising materials for heat dissipation problems.

We propose a new approach to fabricating carbon nanotube (CNT) via interconnects for future LSIs, which uses preformed catalyst nanoparticles to grow the CNTs. A newly designed impactor provided size-classified catalyst particles. For the new approach, we employ a TiN contact layer which is more resistant to oxidation and enables us to form a lower resistance ohmic contact between CNTs and wiring layers. The resultant CNT–via resistance was 0.59 Ω for 2-µm vias, which is the smallest ever reported. We also study the CNT nucleation process using molecular dynamics and discuss how to remove amorphous carbon from the nucleation process. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

We developed a fast dry oxidation process for chemical vapor deposition (CVD) grown multiwalled carbon nanotubes (MWNTs) using short-wavelength UV [vacuum ultraviolet (VUV) light (λmax=172 nm)] irradiation. We introduced carboxyl groups as many as 3% of carbon atoms within 1 min at room temperature using this process. MWNTs with the carboxyl groups were analyzed by attenuated total reflection (ATR) Fourier transform infrared absorption spectroscopy (FT-IR), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The attachment of the carboxyl groups was further confirmed by reacting ferritin molecules with the MWNTs. The developed dry process with a high reaction rate is a powerful tool for the applications of carbon nanotubes in nanoelectronics.

Bimetallic particles of Ti and Co have been used to grow multi-walled carbon nanotubes (MWNTs) to study the effects of Ti on the growth. The particles were generated by laser ablation and size-classified with a differential mobility analyzer. Diameter-controlled MWNTs were grown on a silicon substrate from 5-nm particles by thermal chemical vapor deposition using acetylene at 510 and 610 °C. Titanium has been found to enhance the MWNT growth significantly. There is an optimum Ti fraction for the growth, as confirmed by evaluation of the growth probabilities of MWNTs. A possible mechanism of growth enhancement by Ti is discussed.

We have successfully developed control of the growth mode of carbon nanotubes (CNTs) by using titanium film and its oxidized form, and measured physical properties. The growth mode of CNTs can be controlled by the under layers of catalysts. Obtained CNT films have the site density of 1010 cm-2 for both the base- and tip-growth modes. Measured electrical resistance of 2-µm-diameter CNT-via, mechanical strength, and thermal conductivity for the base-growth mode CNT films were 91.1 Ω, 670 kPa and 291 W/mK, respectively. Better physical properties were observed for base-growth mode CNT films, compared with the tip-growth mode CNT films. In the base-growth mode, one CNT with a TiC contact had an estimated low electrical resistance of 100 kΩ, a high mechanical strength of 5.5 MPa, and a high thermal conductivity of 2400 W/mK.

By using plasma-enhanced chemical vapor deposition (p-CVD), we grew vertically aligned multi-walled carbon nanotubes (CNTs) directly on a nickel-monosilicide layer, without any catalysts other than a metal-silicide layer. The results we obtained are quite important for practical application of CNT vias formed directly on nickel-monosilicide (NiSi) layers, which form the source, drain, and gate region of metal-oxide-semiconductor field-effect transistors (MOSFETs). By using a nickel-silicide layer as a catalyst, the nanotube diameter became smaller than that obtained with a nickel film catalyst. We have also clarified the possibility that CNT diameter can be controlled by forming various Ni-silicide phases such as Ni2Si, NiSi and NiSi2. We suggest that Ni-silicide composition plays an important role in controlling the diameter of the nanotubes. These results will enable us to fabricate CNT vias for future LSI interconnects.

Diameter-controlled multiwalled carbon nanotubes (MWNTs) have been grown by hot-filament chemical vapor deposition using nickel nanoparticles as catalyst. The nanoparticles were generated by laser ablation, classified with a differential mobility analyzer, and deposited onto silicon substrate. The particle size is tunable down to 2–3 nm, and particles with a geometric mean diameter of 5.1 nm (geometric standard deviation: 1.1) were used for carbon-nanotube growth. MWNTs were grown on the substrate using acetylene at 550 °C. The particles did not coalesce during growth, and the MWNTs had outer diameters matching the particle sizes, indicating that the current method can produce diameter-controlled MWNTs.

We have succeeded in making peapod structures with vertically aligned multi-walled carbon nanotubes (MWNTs), grown on a silicon substrate using hot filament chemical vapor deposition. Opening the tips of the MWNTs was performed at 600 ∘C using oxygen and then C60 molecules were deposited on them to fill their inner spaces. We confirmed that the MWNTs were open at the tips and filled with C60 molecules using transmission electron microscopy. In addition, it has been determined that MWNTs can be filled with other materials, such as molybdenum oxide.

We have developed a method of directing or bending carbon nanotubes (CNTs) in the desired direction along a structure. The new method utilizes careful positioning of a catalyst with respect to the structure, so that the CNTs growing from the catalyst experience an effective van der Waals force from the structure. The force causes a CNT-bundle to grow in the desired direction. For instance, a CNT-bundle coming out of a hole can be bent to the right or left depending on the catalyst patterning at the bottom. This approach is promising for achieving three-dimensional CNT wiring for future electronic devices.

We demonstrated that the thinning of InGaP electron supply layers is very effective in reducing short channel effects, even for 0.065 μm gate InGaP/InGaAs/GaAs pseudomorphic HEMTs. By thinning the InGaP electron supply layer to 11.5 nm with a high doped density of 5 × 10 18 cm −3 , we were able to minimize the threshold voltage shift to less than 0.15 V compared to 1.65 μm gate length HEMTs. We could also increase the extrinsic transconductance ( g m ) by thinning the InGaP electron supply layer. We observed no degradation of gate leakage characteristics, regardless of such a highly-doped, thin InGaP layer. The 0.065 μm gate length HEMT exhibits an extrinsic transconductance ( g m ) of 585 mS mm −1 , a current gain cutoff frequency ( f τ ) of 110 GHz and a maximum oscillation frequency ( f max ) of 150 GHz.

During annealing in vacuum and dry O 2 , the amount of suboxide, Θ s , in the 1000 A SiO 2 films on Si(111) was measured as a function of the annealing time by angle-resolved X-ray photoelectron spectroscopy (ARXPS). From ARXPS spectra of Si 2p taken at two polar angles of 0° (bulk sensitive) and 75° (surface sensitive), it was clarified that during annealing in vacuum, Θ s increases with time underneath the surface more largely than on the surface, but annealing in O 2 atmosphere at 0.5 Torr reduces Θ s on the surface more significantly than underneath the surface. These indicate that SiO molecules outdiffusing from the SiO 2 /Si interface are oxidized by permeating O 2 in the SiO 2 films.

We have developed a novel process, the implantation of carbon nanotubes (CNTs) into holes like plugs, vias, and through-silicon vias (TSVs) for the first time. The developed low-temperature process is suitable for back-end-of-line (BEOL) processes of LSI. With this approach, we can use high-quality CNTs grown at high temperature on a different substrate and densify CNTs. Consequently, the implanted CNT plugs had a resistance one order of magnitude lower than the directly grown CNT plugs. In addition, we successfully integrated the implanted CNT plug with transferred multilayer graphene (MLG) wires for all carbon interconnects.

We report numerical simulations of heat dissipation properties of nano-carbon through silicon via (TSV), thermal interface material (TIM), and chip package towards a high heat dissipation LSI 3-D packaging. By using vertically aligned multi-walled CNTs (MWNTs) as both TSV and TIM materials and graphite as chip package, a boundary temperature just under a heat source decreased 40.8K in total, comparing to that using conventional materials. This result suggests superior heat dissipation properties of nano-carbon 3-D packaging.

The Fe/Ti catalyst system that was recently found to be effective for the growth of dense carbon nanotube (CNT) forests was studied using hard x-ray photoemission spectroscopy (HAXPES). It was previously found that the Ti support layer was partially oxidized at room temperature (RT) and absorbed oxygen from the Fe overlayer at higher temperatures, which gave rise to the dense CNT forest growth. The aim of the present study was to elucidate the reason for the initial oxidation of the Ti layer at RT, which remained unclear from the results of the previous study. The control of the initial Ti oxidation is important because it could affect the reduction and activation of the Fe layer at higher temperatures. Depth-dependent HAXPES measurements using different x-ray incidence angles revealed that the degree of oxidation of the 1-nm-thick Ti layer in a sample that had been aged at RT for approximately three months varied depending on the depth. This suggests that oxidation of the Ti layer proceeded after the Fe/...

By using plasma-enhanced chemical vapor deposition (p-CVD), we grew vertically aligned multiwall carbon nanotubes (CNTs) directly on a nickel-silicide layer, which can be used as electrodes for metal-oxide-semiconductor field-effect transistors (MOSFETs). By using a nickel-silicide layer as a catalyst, the nanotube diameter became smaller than that possible with a nickel film catalyst. We suggest that Ni-silicide composition plays an important role in controlling the diameter of the nanotubes. To our knowledge, this is the first report on diameter-controlled vertically aligned CNT growth on catalytic metal-silicide substrates.

This paper reports the tailoring thermal conductivity of novel dense vertical and horizontal graphene (DVHG) structures, which we previously discovered. By removing horizontal graphene layers, resulting in forming vertical graphene contacts to the electrode, we not only improved the thermal conductivity by a factor of 10 but also improved the electrical conductivity by a factor of 100. The pyrolytic graphite, grown at a higher temperature than the DVHG, showed a high thermal conductivity of 1426 W/mK by forming vertical graphene contacts. Although the DVHG showed poor thermal properties at this point, we found that the vertical graphene contact formation can be an important technology to realize high thermal conductivity for carbon-based thermal through-silicon-vias (TSV).

With the aim of achieving low-power consumption, high-performance LSIs, our work focuses on the development of low-resistance carbon nanotube (CNT)/graphene interconnect technologies. For vertical interconnects, we report on a previously unseen dense vertical and horizontal graphene (DVHG) structure, which is expected to lead to a low electrical resistance. For horizontal interconnects, we have succeeded in forming multi-layer graphene (MLG) directly on SiO 2 by annealing sputtered amorphous carbon. Furthermore, achieving low-resistance contacts between the vertical CNTs and horizontal graphene represents a critical issue for 3D interconnects. We grew vertically aligned CNTs on MLG, and analyzed the contact structure using cross-sectional TEM-EELS measurements. Migration of Ti and Co into the graphene layers was clearly observed. This may contribute to the reduction of contact resistance between CNTs and graphene.

We have fabricated multi-layer graphene directly on SiO 2 by annealing sputtered amorphous carbon with a Co catalyst without use of complicated transfer processes. Structural analysis revealed that the graphene sheets formed an epitaxial structure, aligned to the Co (111) surface. An MLG wire can sustain a high current density of 107 A/cm2 which is over one order of magnitude higher than that of a Cu wire.

The thermal oxidation kinetics of Si with dry oxygen was investigated by X-ray and ultraviolet photoelectron spectroscopy. The SiO desorption was found to be maintained for a while even after the oxide growth during initial oxidation. By the annealing of thick oxides in O 2 , the oxidation of SiO molecules in SiO 2 was verified more straightforwardly. Further, it was observed that the decomposition kinetics are closely concerned with the SiO 2 /Si strained interface at 730°C, suggesting that the point defect produced by the strain is responsible for the SiO formation. Based on the observations, a unified thermal oxidation model is proposed, in which oxidation and decomposition always take place simultaneously by vacancies and Si self-interstitials due to point defect generation at the interface, respectively, in addition to the oxidation of SiO by O 2 permeating into SiO 2 . It is pointed out that SiO molecules are so unstable that they diffuse through the repeated exchange reaction of SiO with SiO 2 . Although SiO can be oxidized under O 2 in SiO 2 , SiO would desorb from the SiO 2 surface when the O 2 pressure is too low and in vacuum, leading to the removal of oxide. By the use of the present unified model, one can interpret successfully the 18 O profile measured by SIMS for the oxidi reoxidized with 18 O 2 isotope [J.A. Costello and R.E. Tressler, J. Electrochem. Soc. 131 (1984) 1944] and the initial rapid oxidation below 300 A.

We investigated the mechanism of resistivity decrease in networked-nanographite wires. The wires had no failure during over 200 hours under a current density of 5E5A/cm2 at about 400°C. However, their resistivity decreased gradually owing to thermal stress. Raman and x-ray photoelectron spectroscopy revealed that the decrease in resistivity can be attributed to an increase in sp2 bonding corresponding to the formation of a graphene sheet. It is important to clarify the mechanism for the decrease in resistivity, not only to improve thermal stability but also to obtain lower resistivity in carbon interconnects.

Carbon nanotubes (CNTs) offer unique properties such as the highest current density, ballistic transport, ultrahigh thermal conductivity, and extremely high mechanical strength. Because of these remarkable properties, they have been expected for use as wiring materials and as alternate channel materials for extending complementary metal-oxide-semiconductor (CMOS) performance in future very large scale integration (VLSI) technologies. In this paper, we report the present status of CNT growth technologies and the applications for via interconnects (vertical wiring) and field-effect transistors (FETs). We fabricated CNT via and evaluated its robustness over a high-density current. In our technology, multiwalled carbon nanotubes (MWNTs) were successfully grown at temperatures as low as 365°C using Co catalyst nanoparticles, which were formed and deposited by a custom-designed particle generation and deposition system. The density of MWNTs grown at 450°C reaches more than 1×1012/cm2. MWNTs were grown in via holes with a diameter as small as 40 nm. The resistance of CNT vias with a diameter of 160 nm was found to be of the same order as that of tungsten plugs. The CNT via was able to sustain a current density as high as 5.0×106A/cm2 at 105°C for 100 h without any deterioration in its properties. We propose a Si-process compatible technique to control carrier polarity of CNFETs by utilizing fixed charges introduced by the gate oxide. High-performance p- and n-type CNFETs and CMOS inverters with stability in air have been realized.

We have developed networked-nanographite (NNG) wires as the first step for multilayer graphene interconnects. Photoemission-assisted Plasma-enhanced CVD has been proposed as a growth method on dielectrics without catalysts. The activation energy of carrier conduction for NNG wire was almost the same as that of multilayer graphene exfoliated from highly oriented pyrolytic graphite (HOPG). This means that NNG consists of domains of multilayer graphene. Although we need to improve growth conditions, NNG is one of the candidates for future interconnect materials.

Carbon nanotubes (CNTs) are attractive as nanosize structural elements from which devices can be constructed by bottom-up fabrication. A CNT is a macromolecule of carbon and is made by rolling a sheet of graphite into a cylindrical shape. CNTs exhibit excellent electrical properties that include current densities exceeding 109 A/cm2 and ballistic transport along the tube. Because of these factors, with their large electro-migration tolerance and low electrical resistance, CNTs can be used as nano-size wiring materials, and are thus becoming potential candidates for future LSI interconnects. Much effort has been made to produce CNT vias, which use bundles of MWNTs (multi-walled carbon nanotubes), as vertical wiring materials as shown in Figure 1. Sato et al. demonstrated low-resistance CNT vias employing a novel metallization technology, which used preformed catalyst metal particles, to grow dense MWNT-bundles by thermal chemical vapor deposition (CVD).

We have improved the high-current reliability of carbon nanotube (CNT) via interconnects by chemical mechanical polishing (CMP) and vacuum in situ metal deposition processes. These processes enable us to decrease the contact resistance of a CNT via to the upper and lower Cu lines, and also increase the number of CNTs contributing to current flow. Consequently, the current density per CNT was decreased, and current tolerance properties were improved. As a result, the CNTs via interconnects were able to withstand a high current density of 4×107 A/cm2 per via, i.e., 1.7×108 A/cm2 per CNT. In addition, we found that the failure mode of Cu-line/CNT-via/Cu-line interconnects with a CNT density of 3×1011 tubes/cm2 was the slit void formation at the Cu line under the via, which is similar to that of Cu via interconnects. Furthermore, we discussed how to further increase the tolerance of electromigration (EM), taking advantage of their high thermal conductivity.

We have succeeded in fabricating ultrafine carbon nanotube (CNT) via interconnects with SiOC interlayer dielectrics. High-quality multiwalled CNTs are grown in via holes with a diameter of 70 nm using pulse-exited remote plasma-enhanced chemical vapor deposition at 450 °C. The resistance of a 70-nm-diameter CNT via is 52 Ω, which is the lowest ever reported for CNT via interconnects. The CNT via interconnect has the capability to sustain current density as high as 1×108 A/cm2.

We have fabricated top-gated field effect transistors (FETs) using graphene synthesized by chemical vapor deposition directly on a SiO2/Si substrate without using any transferring processes. Graphene was synthesized on an Fe catalyst film on the substrate at 650°C. The catalyst film was then etched after both ends of the graphene were fixed by source and drain electrodes, leaving the graphene channel connecting the two electrodes. Top-gated FETs were then made by covering graphene channels with HfO2 and depositing top electrodes. The drain current was successfully modulated by the gate voltage and exhibited the bipolar behavior that is characteristic of graphene. Also, it has been shown that graphene channels can sustain an electric current with a density of 107–108 /cm2. Our newly developed fabrication process paves a way to fabricate graphene transistors all over large substrates including Si and glass.