Template synthesis of carbon nanotubes from porous alumina matrix on silicon

The extreme properties of carbon nanotubes (CNTs) make them a good candidate for advanced interconnects to achieve the performances required for the new generation of integrated circuits (ICs). However, the integration of CNTs in microelectronics devices requires the development of a technique allowing the control of the morphology of CNTs. In this paper, we report on a simple technique to vertically integrate CNTs on silicon substrate via porous alumina thin films. The process follows four steps: (i) aluminium thin films deposition on Si substrate, (ii) anodic oxidation generating an alumina template with vertical and cylindrical nanopores (ϕ < 40 nm), (iii) electrodeposition of metal catalyst on Si substrate at the bottom of the pores, and (iv) CNTs growth inside as-formed nanopores by a PECVD technique. It was demonstrated that the quality of the aluminium thin layers is crucial for the control of the oxidation step. Then, the experimental parameters of anodic oxidation (voltage, electrolyte, one or two steps oxidation process, etc.) were tuned to modulate the porosity (pore diameter and density) of the as-formed alumina. The growth of CNTs inside the alumina matrix shows a direct relationship between CNTs morphology and nanopores one.