Methods of fabricating probe cards including nanotubes

A method of fabricating a plurality of carbon nanotube-bundle probes on a substrate, said method comprising:

• providing the substrate having a top surface and a bottom surface;
• forming an array of electrically conductive pads on said top surface, each of said pads including first and second concentric conductive areas electrically isolated from each other by a non-conductive portion of the top surface, said first conductive area being an outer ground ring and said second conductive area being an inner signal pad that is a substantially solid circle;
• applying a catalyst for promoting growth of carbon nanotubes on each of said first and second concentric rings of each pad of said array of electrically conductive pads;
• and
• heating said substrate in a carbon-rich environment thereby growing nanotubes extending upwardly from each of said first and second concentric rings of each pad of said array of electrically conductive pads thereby forming an array of concentric nanotubes extending upwardly from said first and second concentric rings of each pad, wherein a common bus electrically connects the outer ground ring members of the array.