Contact resistances of carbon nanotube via interconnects

We present an extensive characterization of carbon nanotube (CNT) via interconnects grown under various conditions, with particular focus on contact resistance. Si process-compatible elements Ti, Cr, and Al are used as underlayer metals, together with the two most effective catalysts Ni and Fe, to study the growth behaviors and contact resistances of vertically aligned CNTs. The CNT via test structure is designed and fabricated for current-voltage measurements on individual CNTs using atomic force microscope (AFM) current-sensing technique or in situ nanoprobing during scanning electron microscopy (SEM) imaging. By analyzing the dependence of measured resistance on CNT diameter, the CNT-metal contact resistance can be extracted. Relationships between contact resistances and various combinations of catalysts and underlayer metals are investigated.