Growth of CNTs on graphene for future 3D-IC

• Main Author: Hagi, Theodore
• Other Authors: Tay Beng Kang
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Electrical and electronic engineering
• Online Access: http://hdl.handle.net/10356/71827
• Institution: Nanyang Technological University

This project is a part of a research project to realise a combined Graphene and CNTs interconnect to replace copper based interconnect for 3D Integrated Circuit. Graphene and CNTs have shown potential to be a replacement of copper interconnect, which suffer increase of resistivity for dimension below ~39 nm. In this project, the growth of Carbon Nanotubes on Graphene was studied. Carbon Nanotubes were grown using TCVD system with C2H2 carbon feed gas and Fe catalyst. Optimisation of the growth was done by modification of growth temperature, catalyst thickness, presence of buffer layer, and process steps to obtain a longer CNTs on Graphene. Characterisation of the samples were done with SEM and Raman Spectroscopy. The dependence of additional process steps, which include sample annealing, Pre-Growth of CNTs, and Post-Growth of CNTs to the length of grown CNTs were analysed. The dependence was observed with limited samples grown, hence the results might not be conclusive. Longest CNTs were observed for growth temperature of 700ºC compared to growth done at 675ºC and 725ºC. In lower temperature, the carbon feed gas were not completely dissociated, while in higher temperature, the hydrogenation etching effect occurs. From experimental results obtained, catalyst thickness of 1 nm results in longer CNTs grown compared to using catalyst with thickness of 2nm. The difference varies up to 6x for Graphene substrate with a buffer layer. The presence of buffer layer is shown to be necessary to realise a highly uniform and dense CNTs forest on Graphene substrate. Lack of buffer layer produce CNTs grown in patches on the substrate. The detailed explanation of parameter dependence will be provided in this report.