We propose a new approach to fabricating carbon nanotube (CNT) vias, which uses preformed catalyst nanoparticles to grow CNTs. A newly-designed impactor provided size-classified catalyst particles, and a new deposition system injected them into via holes down to 40 nm in diameter. The resultant CNT-via resistance was 0.59 Ω for 2-µm vias, which is the lowest ever reported, improved from the previous studies using catalyst films. The improvement resulted from higher-density CNTs grown in the via holes by employing the nanoparticle catalyst.

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Carbon nanotubes (CNTs) have been successfully developed as thermal and source bumps for flip-chip high power amplifiers (HPAs). The newly developed 15 µm long CNT bumps exhibit thermal conductivity of 1400 W/m⋅K. A flip-chip AlGaN/GaN HEMT HPA with a gate width of 2.4 mm utilizing CNT bumps, operating voltage of 40 V, exhibits an output power of 39 dBm at a frequency of 2.1GHz without any degradation due to heat-up. To our knowledge, this is the first report about a practical application of CNTs using their high thermal conductivity.

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