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Graphene and carbon nanotubes (CNTs) are both carbon-based materials with remarkable optical and electronic properties which, among others, may find applications as transparent electrodes or as interconnects in microchips, respectively. This work reports on the formation of a hybrid structure composed of a graphitic carbon layer on top of vertical CNT in a single deposition process. The mechanism of deposition is explained according to the thickness of catalyst used and the atypical growth conditions. Key factors dictating the hybrid growth are the film thickness and the time dynamic through which the catalyst film dewets and transforms into nanoparticles. The results support the similarities between chemical vapor deposition processes for graphene, graphite, and CNT. [ABSTRACT FROM AUTHOR]

Electrodeposition is an excellent method for a site-selective and direct fabrication of catalyst nanoparticles for subsequent carbon nanotube (CNT) growth. Nickel nanoparticles with densities as high as 1011 cm-2 and diameters down to 15 ± 4 nm are deposited on blanket and pattemed TiN wafers. Ni nanoparticles are selectively placed at the bottom of submicrometer vias by through-mask electrodeposition. The spherical nanoparticles all produce aligned multiwalled CNTs. The CNT diameter is directly determined by the diameter of the as-deposited nanoparticles, which is tailored by the electrodeposition conditions. Such control of CNT size, density, and location represents an important step toward the implementation of CNTs in device fabrication. [ABSTRACT FROM AUTHOR]

We investigate colloidal Fe3O4 nanocrystals as a catalyst system for carbon nanotube (CNT) growth that allows for decoupling the CNT growth step from the catalyst shaping and activation step. The system consists of 6.4 nm Fe3O4 nanocrystals synthesized using a solution-based thermal decomposition reaction and, subsequently, transferred as hexagonally ordered Langmuir–Blodgett (LB) monolayers on TiN substrates. We demonstrate for the first time aligned CNT growth from LB deposited nanocrystals on a metallic underlayer. The hexagonally ordered monolayers of catalyst particles show promising stability up to the CNT growth temperature. In situ TEM heating experiments were performed to find this onset of particle deformation and showed stability of the nanoparticles up to 600 °C. The particle coalescence at high temperatures was also evidenced by the increasing CNT diameter, from 9.5 nm at 580 °C to 16 nm at 630 °C. By choosing to work at temperatures below the onset particle coalescence temperature, equivalent CNT diameters were obtained under different catalyst activation and growth conditions. The high stability of the catalyst on the metallic underlayer enables us to study CNT growth kinetics independently of the catalyst shaping step. This work opens a route towards combining growth studies with an electrical evaluation of the CNT growth as the TiN can be used as the bottom contact. [ABSTRACT FROM AUTHOR]

Highlights: [•] One MWCNT per contact hole meets ITRS conductivity requirement for sub-15nm DRAM contact technology. [•] Termination of CNT growth limits CNT length below 500°C. [•] Improved CNT contact resistance and yield across 200mm wafer upon adding ALD Al2O3. [•] Catalyst particle density close to 1012 cm− 2achieved on TiN. [ABSTRACT FROM AUTHOR]

Abstract: Carbon nanotubes (CNTs) were integrated successfully into 150nm contact holes having a TiN underlayer and a Cu single damascene top contact module. All the integration steps for CNT integration, for patterning the Cu top contact and the mask-set used are compatible with 130nm device technologies on 200mm wafers. The first resistance yield plots for the CNT contacts on full wafer level are presented. For CNT grown at 540°C in contact holes with aspect ratio 1.3, a single CNT contact hole resistance of 3.4kΩ was achieved. The structure designed, the process flow presented here for CNT integration, and the automatic probing constitute a platform that allows benchmarking different recipes and process conditions. This constitutes a significant step forward towards the realization of a contact module with vertical CNT interconnects of superior quality. This is because the platform can speed up the learning cycle time for optimizing the CNT interconnect based on learning from the electrical performance. [Copyright &y& Elsevier]

Abstract: We propose to use carbon nanotube (CNT)–CNT contacts instead of CNT–metal contacts as a route towards low resistance CNT horizontal interconnects. We characterize by electrical transport measurements and Kelvin probe force microscopy the contacts present in CNT horizontal interconnects grown by chemical vapor deposition between titanium nitride electrodes. When two CNTs with diameter around 30nm grow from opposing electrodes and touch each other with their outermost shells, typical contact resistances around 16kΩ are obtained. The corresponding contact resistivity of about 14Ωμm2 is one order of magnitude smaller than the contact resistivity of a CNT touching the TiN surface with its outermost shell. On the other hand, the contact resistance of a CNT grown from a nickel catalyst particle deposited on a TiN electrode is negligibly small when compared to the above mentioned contact resistances. Our results demonstrate that we are able to grow from opposing electrodes CNTs that touch each other with a corresponding high density (up to 1011 cm−2) of CNT–CNT contacts. This may offer an effective solution towards the growth of low resistance CNT horizontal interconnects. [Copyright &y& Elsevier]

Abstract: Carbon nanotubes (CNTs) are considered a promising material for interconnects in the future generations of microchips because of their low electrical resistance and excellent mechanical stability. In particular, CNT-based contacts appear advantageous when compared with current tungsten or copper technologies and could therefore find an application as metal contacts interconnecting the transistors with the back end of line of the microchip. In this work, the integration of vertical CNT bundles in sub-micron contact holes is evaluated at wafer scale and the major integration challenges encountered in the practical realization of the process are discussed. Nickel PVD films were used to selectively grow CNT into the contact holes at temperatures as low as 400°C, which is the thermal budget available for contacts. The height of the contacts and the length of the CNT are controlled by a chemical mechanical polishing step (CMP) after embedding the CNT into SiO2. Ti/Au metal pads are then formed onto the CNT bundles by PVD and lift-off. The integrated CNT are electrically characterized and an annealing treatment was found to improve the CNT-via resistance. As the electrical properties of the CNT can be evaluated, the structure and the process presented constitute a test vehicle for the development of high-quality CNT-contacts. [Copyright &y& Elsevier]