Takayuki Iwasaki

Low temperature grown carbon nanotube interconnects using inner shells by chemical mechanical polishing

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.

Electrical Properties of Carbon Nanotubes Grown at a Low Temperature for Use as Interconnects

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 Ω for 2-µm-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.

Enhanced field emission properties of vertically aligned double-walled carbon nanotube arrays

Vertically aligned double-walled carbon nanotube (VA-DWCNT) arrays were synthesized by point-arc microwave plasma chemical vapor deposition on Cr/n-Si and SiO(2)/n-Si substrates. The outer tube diameters of VA-DWCNTs are in the range of 2.5-3.8xa0nm, and the average interlayer spacing is approximately 0.42xa0nm. The field emission properties of these VA-DWCNTs were studied. It was found that a VA-DWCNT array grown on a Cr/n-Si substrate had better field emission properties as compared with a VA-DWCNT array grown on a SiO(2)/n-Si substrate and randomly oriented DWCNTs, showing a turn-on field of about 0.85xa0Vxa0µm(-1) at the emission current density of 0.1xa0µAxa0cm(-2) and a threshold field of 1.67xa0Vxa0µm(-1) at the emission current density of 1.0xa0mAxa0cm(-2). The better field emission performance of the VA-DWCNT array was mainly attributed to the vertical alignment of DWCNTs on the Cr/n-Si substrate and the low contact resistance between CNTs and the Cr/n-Si substrate.