Formation and assembly of carbon nanotube bumps for interconnection applications

A simple assembly process of carbon nanotube (CNT) bumps which could be used for flip chip interconnects was proposed and investigated. Firstly, high density aligned CNT bumps were grown on both top and bottom substrates. By employing typical flip chip bonding technique, the CNT bumps on the flipped top substrate were aligned with those on the bottom substrate. Applying a downward force on the die, the CNT bumps on the top substrate were pressed and inserted into the CNT bumps on the bottom substrate. After CNT insertion, the CNTs were held together with van der Waals force and the CNT interconnection bumps were formed. The electrical conductivity of the CNT interconnection bumps was measured and compared to conductive silver adhesive. The conductivity of CNT interconnection bump was found to be of many magnitudes higher than that of silver adhesive. It was demonstrated that the CNT bumps have a much superior electrical properties over the typical metallic bumps.