Contact resistance reduction of carbon nanotube via through O2 plasma post-synthesis treatment

Abstract

The cause of high contact resistance between carbon nanotube (CNT) filled vias and metal electrodes is studied. Contamination due to the chemical–mechanical polishing (CMP) process, which damages the sp² bonds at the end of the CNTs, is found to be the main cause. An alternative oxygen plasma etching process is proposed to preserve the sp² bonds at the CNT tips during the via planarization process. The improved properties of the CNT tips, with more sp² bonds and fewer oxygen-containing groups, have been demonstrated using X-ray photoelectron spectroscopy (XPS). Based on the findings, a new CNT via integration process is designed, which includes selective CNT growth inside the via and O₂ plasma planarization. A low contact resistance of 1.83 μΩ cm² is demonstrated.