Carbon Nanotube Based Interconnect Material for Electronic Applications

Doctoral thesis, 2015

Carbon nanotubes (CNTs) are considered as a candidate material for future electronic interconnect applications. This thesis summarizes the research work on the fabrication and characterization of CNT-based interconnect systems, and explores the possibilities of integrating CNTs into various electronic interconnect scenarios. CNT material properties and fabrication methods are introduced as well as its potential for solving the future interconnect challenges. The technology development works are presented in detail in four categories: synthesis, densification, coating and transfer. The principles of the chemical vapor deposition (CVD) method for producing the CNTs are described and discussed. Densification methods are developed in order to increase the volume density of the pristine porous CVD-grown CNTs. Two techniques, vapor-based densification and paper-mediated wet densification, have been proposed and characterized. CNT transfer techniques are developed in order to decouple the harsh CVD growth environment from the target application devices. Two kinds of transfer medium materials, indium and polymer, have been proposed and optimized. To improve the electrical performance of the pristine CNTs, metallic coating techniques for both vertically aligned and randomly dispersed CNTs are developed and characterized. Finally, three different CNT-based interconnect scenarios: bumps, through silicon vias, and flexible conductors, are demonstrated and characterized, using the as-developed processes. The integration technologies developed in this thesis not only improve the CNT process compatibility with the conventional electronics manufacture flows, but also offers state-of-the-art electrical and mechanical performance for the non-conventional flexible and stretchable interconnect applications.