Solution-Based Fabrication of Carbon Nanotube Bumps for Flip-Chip Interconnects

A reliable solution-based process to fabricate thick carbon nanotube (CNT) bumps has been developed and is presented in this paper. In contrast to other work of this nature, the process we have developed is capable of fabricating thick and densely packed CNT structures at room temperature with relatively high resolution and controllable film thickness or bump height. CNT structures fabricated using the developed method may find use in sensors or electrical interconnect applications. Raman spectroscopy was used to characterize the fabricated CNT bumps, verifying the CNTs are negligibly affected by the fabrication process. To study the potential application of these CNT bumps for flip-chip interconnections, we examined the deformation of the CNT bumps after flip-chip bonding and performed electrical characterization. The CNT bump interconnects display linear I-V curve with an average resistance of approximately 484 mΩ for a bump with 200 μm diameter and height of 12 μm. Temperature-dependent measurements indicate that fluctuation-induced tunneling (FIT) is the most likely electrical conduction mechanism in the CNT bumps.