Carbon nanotube bumps for LSI interconnect

We demonstrate, for the first time, carbon nanotube (CNT) flip chip bumps for LSI modules. The CNT bump is composed of a bundle of multi-walled CNTs. Resilient and flexible CNT bumps make flip chip LSI modules resistant to thermal stress. Furthermore, CNT bumps have a low electrical resistance and robustness over electromigration. In the experiment, the CNT bumps were used to connect a test evaluation group (TEG) chip and a host substrate, and their electrical resistance was evaluated. We found that the electrical contacts of CNT bumps with the chip and the substrate are important. For a good electrical contact, the CNT bumps were coated with gold and fixed to the chip and substrate. The resultant CNT bump with a diameter of 170 mum and a height of 100 mum exhibited a low resistance of 2.3 Omega. We then evaluated the flexibility of CNT bumps by pressing the TEG chip and measuring the displacement. The displacement between the TEG chip and host substrate was 10-20% of the bump height, demonstrating an excellent flexibility.