Integration of Vertical Carbon Nanotube Bundles for Interconnects

Abstract

Carbon nanotubes ͑CNTs͒ are considered a promising material for interconnects for future generation microchips. The integration of vertical CNT in a processing environment is evaluated in this work. Extrapolated performances of CNT-based interconnects are compared with existing technologies at different hierarchy levels including the limitations of present deposition methods for copper and tungsten. For practical implementation, CNT bundles were selectively grown into contact holes using physical vapor deposited and electrochemical deposited cobalt or nickel catalysts. A polishing step was used to control the CNT length after embedding the CNT into an oxide matrix. A CNT metal decoration method based on electrodeposition is presented, which can be used to assess the yield of electrically conductive CNT as well as to form top contacts for electrical characterization. Finally, the importance of having suitable and robust structures for evaluating the integration process is highlighted after the electrical characterization of CNT in a nanoprober station.

Integration of CNT in TSV (≤5 μm) for 3D IC application and its process challenges

“…This is due to the fact that via PVD process of catalyst deposition is not spatially selective as it allows deposition of catalyst anywhere inside the TSV hole. The CNTs from the TSV sidewall is not at all expected [9] because they do not form electrical contact with both end of metal lines at the bottom of the TSV in actual application.…”

“…However, sometimes the measured CNT density under SEM technique is as accurate. Thus, IMEC [9] recently demonstrates that one of the alternate possibilities is to grow the CNT bundles on top of the metal lines followed by CMP and electroplating to deposit metal at highly reactive dangling CNT tips. By this process metallic particles are formed only on those CNTs that are in electrical contact with the bottom metal lines.…”

Characterization of contact resistances in ceramic-coated vertically aligned carbon nanotube arrays

“…On a device scale, the ensemble-averaged, endcontact resistance per nanotube can be obtained from a polished VACNT forest less than a micrometer in height. 17,31,32 This approach loses accuracy the taller the CNT forest (tall CNT forests offer higher mass loading in electrochemical devices 33 ) because their lengths become the more heterogeneous. 34,35 Here, we establish characterization methods for both sideand end-contact resistances of VACNT forests (Fig.…”

Electrical and structural characterization of 150 nm CNT contacts with Cu damascene top metallization

“…With diameters > 1 nm, this nanomaterial can already have outstanding electronic properties such as room temperature ballistic charge transport over micrometer length scales, a high thermal conductivity, and an excellent resistance to high current densities [2]. Combined with its bottom up growth process, bundles of dense CNT (> 10 12 cm -2 ) [3] can be attractive for filling high aspect ratio structures and a single multi-walled CNT can offer a filling solution for sub 11 nm contact dimensions [4]. For these reasons, current research efforts are focusing on growing dense CNTs and the integration of this new material into contacts [5].…”