Measuring the electrical resistivity and contact resistance of vertical carbon nanotubebundles for application as interconnects

Abstract

Carbon nanotubes (CNT) are known to be materials with potential for manufacturingsub-20 nm high aspect ratio vertical interconnects in future microchips. In order tobe successful with respect to contending against established tungsten or copperbased interconnects, though, CNT must fulfil their promise of also providing lowelectrical resistance in integrated structures using scalable integration processes fullycompatible with silicon technology. Hence, carefully engineered growth and integrationsolutions are required before we can fully exploit their potentialities. This worktackles the problem of optimizing a CNT integration process from the electricalperspective. The technique of measuring the CNT resistance as a function ofthe CNT length is here extended to CNT integrated in vertical contacts. Thisallows extracting the linear resistivity and the contact resistance of the CNT, twoparameters to our knowledge never reported separately for vertical CNT contactsand which are of utmost importance, as they respectively measure the qualityof the CNT and that of their metal contacts. The technique proposed allowselectrically distinguishing the impact of each processing step individually on theCNT resistivity and the CNT contact resistance. Hence it constitutes a powerfultechnique for optimizing the process and developing CNT contacts of superiorquality. This can be of relevant technological importance not only for interconnectsbut also for all those applications that rely on the electrical properties of CNTgrown with a catalytic chemical vapor deposition method at low temperature.