Carbon nanotube vertical interconnects fabricated at temperatures as low as 350 °C

Carbon nanotube (CNT) vertical interconnects (vias) were fabricated on conductive substrates at a record-low temperature of 350 °C, using only standard semiconductor manufacturing techniques and materials. CNT growth rates were investigated for both Co and a Co–Al alloy catalysts, and compared to that of Fe. The activation energy of the Co-based catalysts was found to be lower, allowing lower temperature growth. Using Co as catalyst full-wafer CNT test vias were fabricated at 350 °C, and 400 °C, and electrically characterized. Good uniformity was obtained, with no apparent yield-loss compared to higher temperature fabricated CNT vias. A negative thermal coefficient of resistance was observed of −800 ppm/K, which is advantageous for interconnect applications. The resistivity of the vias increases with temperature, up to 139 mΩ cm for 350 °C, but was found to be lower than several values obtained from literature of CNT vias fabricated at higher temperatures.