Development of carbon nanotubes for interconnection applications
Yung, Wendy Ka Po
Date of Issue2009
School of Electrical and Electronic Engineering
This thesis records the development of carbon nanotubes (CNTs) material, fabrication techniques and process for interconnection application in very-large-scale integration (VLSI) and flip chip interconnects. For CNT to be used as VLSI interconnect, a self assembly fabrication technique for joining individual CNT into a three dimensional (3-D) CNT network is developed using a simple two steps plasma enhanced chemical vapor deposition (PECVD). Electrical transport property of the 3-D CNT network within a polystyrene matrix was found to exhibit electron tunneling conductivity. The finding indicates that CNTs in the network are well joined with ohmic contact. A simple process for joining CNT bumps is also developed, which is applicable in the first level flip chip interconnect. In this method, the die and carrier are assembled by applying a downward force to the die and forcing the CNT bumps on die to be “inserted” into the ones on its carrier. Electrical measurement was conducted on the assembled CNT structure and was found to be of many magnitudes higher than the conductivity of silver paste. CNT VLSI on-chip interconnect and CNT flip chip first level interconnect fabrication process using the two CNT joining techniques are also proposed. To synthesis CNTs with desired structures, investigation on the effects of different deposition conditions, catalyst and catalyst support layers on the nanotubes grown were conducted. In the first study, the effects of C2H2 concentration, deposition time, temperature and working pressure on non-aligned CNT growth by hot filament chemical vapor deposition (HFCVD) were investigated. It was realized that deposition temperature had the most significant effect on CNT growth rate. An increase in film thickness suffered from reducing density in the case of increased C2H2 concentration, deposition time and deposition temperature. Higher working pressure led to the growth of denser and longer nanotubes. Aligned CNT growth on varied thickness of nickel catalysts by HFCVD and PECVD is also studied. It was found that catalyst thickness has significant effects on the diameter of the nanotubes.
DRNTU::Engineering::Electrical and electronic engineering::Nanoelectronics