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|Modeling and Optimization of Bond Wires as Transmission Lines and Integrated Antennas at RF/Microwave Frequencies|
|Keywords: bond-wire, antenna, transmission-line|
|For about three decades now, wire-bonding has been the most widely used chip-interconnection method. Consequently, much research efforts have been dedicated to study the electrical, thermal and thermo-mechanical properties of bond-wires. Concerning the electrical properties, the length of bond-wires and hence, their inductance, has been the limiting factor for their application as "transmission lines" at upper RF/microwave frequencies. This inductance depends on the return-current path. Therefore, as our first goal, we studied the impact of the return-current path on the inductance and RF performance of bond-wires. Beginning with a single signal bond-wire having its return-current over a ground plane, we systematically increased the number of bond-wires to two (i.e., ground and signal) and 3 (ground-signal-ground) with/without a ground plane in the vicinity of the wires. Considering a bond-wire having a diameter of 25 microns and length of 1mm, we optimized the return-current path, such that the bond-wire could be used as a "transmission line" with less than 10% signal distortion up to 10 GHz. Our second goal is to make use of the length of bond-wires, which posses the greatest barrier for their application as "transmission-lines" at upper RF/microwave frequencies. The motivation behind this idea is that, due the huge signal degradation associated with conventional signal paths in microelectronic systems, it will be very challenging to interconnect very high-speed multi Gb/s chips within such a system using traditional routing. Therefore, novel concepts where the chips are connected via wireless links have already been proposed. However, up to date, only conventional planar antennas have been used. In this work, we propose the use of bond-wires as integrated antennas for chip-to-chip communication. We designed and simulated a monopole bond-wire antenna and also investigated the impact of the integration of this antenna. Very good radiation characteristics were obtained for 60 GHz applications.|
|Dr. Ivan Ndip, Group Manager
Fraunhofer Institute for Reliability and Microintegration (IZM)