Carbon nanotube based via interconnects: Performance estimation based on the resistance of individual carbon nanotubes

Carbon nanotube (CNT) based interconnects with an improved bottom metallization scheme were prepared and characterized. Two procedures are introduced to enhance the CNT via performance after planarization. Both, temperature annealing of the metal-CNT contact and exposing the CNT tips to HF vapor prior to the deposition of the top metallization increased the yield and reduced the resistance of the vias. For a via of 5 µm diameter and a depth of 800 nm a resistance of 8 ohm was obtained. Further, the resistance of individual CNTs was measured by means of conductive atomic force microscopy (cAFM), giving a value of 38 kohm/CNT. We highlight the capability of cAFM to accurately predict the overall electrical performance of CNT based vias. Deviations of the measured resistance compared to the theoretical limit are either attributed to defects in the CNT's atomic structure or imperfect contacts. To separate those two aspects, different methods to investigate the microstructure of the employed materials were used.