Chemical Transfer of in-situ Functionalized Aligned Carbon Nanotube Structures for Microelectronic Packaging Applications

As IC performance increases, many technical challenges appear in the areas of current-carrying capacities, thermal management, I/O density, and thermal-mechanical reliability. To address these problems, the use of aligned carbon nanotubes (CNTs) has been proposed in IC packaging for electrical interconnect and thermal interface materials (TIMs). The theoretically superior electrical, thermal, and mechanical properties of CNTs promise to reduce the interconnect pitch size, increase thermal conductivity, and enhance system reliability, which is expected to bring about revolutionary improvement to microelectronics. However, the problems with the CVD growth process such as high growth temperature and poor adhesion of CNTs to substrates, challenges in selectively patterning CNT structures and high contact resistance of CNT/electrodes become barriers for CNT applications. To circumvent these problems, great efforts have been made to separate the CVD process and the ACNT assembly by various ACNT transfer technology with moderate success. For the popular wet chemical process, pristine CNTs are functionalized in acids and then assembled onto the substrate in a solution. The functionalization process usually truncates the CNTs randomly and introduces high defect density to the lateral walls of the CNTs, which greatly degrades the intrinsic electrical and thermal properties of the 1-D structure of the CNTs. Furthermore, big challenges exist in selective patterning, length control and quality control of functionalized ACNTs. In this study, we proposed the "chemical transfer" method to directly assemble aligned CNTs onto gold-coated substrates.