Novel Enabling Wire Bonding Technology

The microelectronics industry extensively uses wire bonding as a means of interconnecting bond pads on the die to the bond pads on a substrate using thin wires. Wire bonding of gold is mostly used in small signal devices because of gold's ability to be drawn into small-diameter wires (25.4 μm). However, the next generation of wires will need to interface with smaller bond pad structures and provide the required performance and compatibility with "molecular devices". Lithographically-made nanowires can be used as interface but doing so would be very expensive. This paper addresses the next generation of non-lithographically-made nanowire formation and bonding, which will provide a low cost option for dealing with the current trend towards increased I/O and higher reliability. The key point of the paper is the development of a "meet-in-the-middle" technology where functionalized electrospun polymer nanofibers deposited directly on die bond pads may substitute or compliment future wire bonding techniques. The scope of the paper is to demonstrate the manipulation of single non-conductive nanofibers functionalized as conductive nanowires to interconnect nanoscale bond pads on the die to the bond pads on a substrate. Two general schemes for manipulation of single nanowires are presented for diameters from 50 nm to 500 nm. Both schemes are based on the electrospinning technique of nanofibers and their subsequent post-processing. The techniques examined are Near-Field Electrospinning (NFES) and Micro-Bead Electrospinning (MBES).