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.

We measured the electrical properties of vertically aligned carbon nanotubes (CNTs) synthesized from via holes by radical chemical vapor deposition at a low temperature of 390 C, which meets the requirements of the Si large scale integration (LSI) process. To use the CNTs could be used for LSI wiring, we applied chemical mechanical polishing (CMP) to the CNTs and successfully reduced the via resistance by a factor of ten. In addition, the resistance of the CNTs was reduced further to 0.6 for 2-mm-diameter vias by annealing at 400 C. Although the temperature dependence of the resistance of the CNTs grown in vias (CNT-vias) did not indicate ballistic transport, which is one of the expected properties of CNTs, we found that CMP and annealing are effective for reducing the via resistance of CNTs.

Multiwalled carbon nanotubes (CNTs) have been grown by remote plasma-enhanced chemical vapor deposition at temperatures as low as 400 C. In via formation, the selective growth of CNT bundles in via holes at 430 C and chemical mechanical polishing for planarization have been performed. The electrical evaluation of CNT single vias with various diameters reveals that the via resistance is inversely proportional to the via area. This result indicates that the CNTs are grown with uniform quality and density in the via holes with various diameters and stable contact formations are obtained. Moreover, the resistances of single vias are approximately equivalent to the via resistances estimated from the resistances of via chains, demonstrating the via-to-via uniformity of the CNT vias obtained by the remote plasma-enhanced chemical vapor deposition.

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A planar circulator circuit (PCC) implementing a 180 hybrid circuit for reflection-geometry sub-terahertz-wave imaging has been developed. The PCC is evaluated by measuring its signal transfer characteristics at around 300 GHz. A resonant behavior with a unidirectional cycling transmittance is observed in the PCC at around 270 GHz, indicating the proper function of the PCC as a circulator. The peak signal-to-background ratio is measured to be about 10. The PCC is integrated with a uni-traveling-carrier photodiode and a Schottky barrier diode to construct a photonic transceiver module. The characteristics of the PCC in the module are also evaluated by measuring images of a test sample. Although the image resolution decreases with signal frequency deviation from the resonant condition, it is confirmed that a practical contrast can be obtained for a bandwidth of about 40 GHz. Using the fabricated transceiver, the in vivo imaging of a human finger at 270 GHz is successfully demonstrated.