Growth of aligned carbon nanotube arrays for electrical interconnect

As IC performance increases, many technical challenges appear in the areas of power delivery, thermal management, I/O density, and thermal-mechanical reliability. To address these problems, the use of aligned carbon nanotubes (CNTs) is proposed in IC packaging as electrical interconnect and thermal interface materials. The superior electrical, thermal, and mechanical properties of CNTs promise to bring revolutionary improvement in reducing the interconnect pitch size, increasing thermal conductivity, and enhancing system reliability. Carbon nanotubes (CNTs) are the fascinating one-dimensional molecular structures that can be either metallic or semiconducting, depending on their diameter and helicity. In order to create interconnect structures comprised of CNTs units, it is necessary to control both the growth of CNTs in predefined orientations and configurations, and the interface with other materials such as metal electrodes. In this paper, we reported a very efficient method to grow well-aligned CNT arrays for intended electrical interconnect paths. A lift-off process was used to pattern catalyst (Al₂O₃/Fe) islands to diameters of 13 or 20 mum. After patterning, chemical vapor deposition (CVD) was involved to deposit highly aligned CNT arrays using ethylene as the carbon source, and argon and hydrogen as carrier gases. The as-grown CNTs were characterized by high resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), and Raman spectroscopy. The feasibility of ACNT interconnect was investigated through the study of CNT/solder interface after a solder reflow process. Preliminary results indicated that molten Sn/Pb solder could wet the CNT surface and form good solder joints. The ACNT structures are proposed to develop ultra-fine pitch electrical interconnections and high thermally conductive interface materials