Flip Chip Based on Carbon Nanotube–Carbon Nanotube Interconnected Bumps for High-Frequency Applications

This paper presents a flip-chip structure based on carbon nanotube (CNT) interconnected bumps for high-frequency applications. The CNT bumps are grown directly on gold coplanar lines using the plasma-enhanced chemical vapor deposition approach, and the CNT bumps are interconnected using a flip-chip bonder. DC and high-frequency measurements from flip-chip input to output are characterized and compared against electromagnetic simulation of CNT bumps and gold bumps. S-parameter transmission of -2.5 dB up to 40 GHz was obtained using CNT bumps in this experiment. Experimental transmission across the CNT bumps demonstrates the feasibility of using CNT bundles for future interconnects at smaller scale (few micrometers) and at even higher frequencies. This is the first work using CNT bumps for flip-chip structures and serves as a platform for future studies of CNT interconnects above 40 GHz.