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Vertically aligned multiwalled carbon nanotubes (MWCNTs) were synthesized by remote plasma chemical vapor deposition at a low temperature of 390°C, which meets the requirement of the large scale integration (LSI) process. For wiring application, we measured the electrical properties of MWCNT-via structures with and without chemical mechanical polishing (CMP). The via resistances were reduced using inner shells of MWCNTs whose caps were opened due to CMP. The improved resistance after annealing at 400°C was 0.6Ω for 2μm vias. Our process is suitable for LSI because the temperature never exceeds the allowable temperature of 400°C in the Si LSI process.

To clarify the effect the oxygen has on the carbon nanotube (CNT) growth mechanisms, the authors use infrared absorption spectroscopy for the monitoring of CNT growth on cobalt catalyst surfaces. CNT grew when methanol was used as a reaction gas, while they did not grow when methane was used. The authors observed spectral changes due to the formation of cobalt oxides and methoxides on the cobalt catalyst surfaces only during the growth of CNT. The results indicate that partial oxidation of the cobalt catalyst surface increases the adsorption probability of the reaction gas and ultimately induces growth of CNT.