The fabrication of ultra long metal nanowire bumps and their application as interconnects

A process of ultra long metal nanowire bumps directly fabricated on a Si die and organic substrate has been developed. Typically, ultra long copper nanowire arrays were electroplated on the conductive pads of both a silicon die and organic substrate with matching peripheral row pads at 200 µm pitches using an anodic aluminum oxide (AAO) template. The nanowires have an average diameter of 200 nm and lengths of about 30 µm. After removing the template, nanowire bumps both on the silicon die and organic substrate have been obtained. A proof of concept of using these metal nanowire bumps as compliant z-axis interconnects is presented. Nanowire to nanowire interweaving “Velcro” (http://www.velcro.com) type contact is established by lowering the die onto the substrate using a flip-chip bonder under controlled force. It was observed that the “Velcro” type of interconnect has been enhanced by dispensing and curing a polymer material between the die and the substrate. A single mating pair of nanowire interconnects has been measured using a 4-point Kelvin probe method. This Velcro type of interconnect can be fabricated at a low temperature (depending on the polymer curing temperature) which may be advantageous for organic electronics, in 3D integration of stacked chips or other temperature sensitive interconnect applications.