A method to form self-aligned carbon-nanotube-vias using a Ta-cap layer on a Co-catalyst

A method to form self-aligned carbon nanotube (CNT) vias using a Ta-cap layer on a Co catalyst by chemical vapor deposition at 400 °C is described. The Ta-cap layer protects the Co catalyst from oxidation. This protection potentially eliminated the need for additional processing steps to control the size and activity of the Co catalyst, which are two critical parameters for CNT formation. The Ta-cap layer was observed to remain on the top of the multi-walled CNTs as a contact layer after the synthesis at 400 °C. The Ta-cap layer self-formed a continuous interface between the electrode layer and the CNT layer. Besides, it can avoid the conventional chemical mechanical polishing process. The Ta-cap layer thickness was found to be the key parameter affecting CNT growth and was optimized. O2 plasma treatment was implemented to remove residual amorphous carbon accumulated on the top of Ta-cap layer after CNT formation. The electrical properties were also measured to verify the feasibility of this CNT-via structure.