Design and Measurement of Interconnects in Fan-Out Wafer-Level Packaging (FOWLP) for mm-Wave Applications up to 100 GHz

This paper presents the results obtained by the design, fabrication and measurements of redistribution layer (RDL) interconnects in Fan-Out Wafer-Level packaging (FOWLP) technology, including straight and bend transmission lines and through layer transitions designed in grounded coplanar wave guide (GCPW) type. The interconnection structures were fabricated in polymer based thin-film technology using 3µm copper sheets separated by 6 µm polyimide layers and providing a minimum lateral line/space of 9µm /9 µm. Measurement results up to 100 GHz are compared to simulation results of both the nominal designs and those fitted to the real geometrical dimensions of the fabricated structures. Surface roughness of the fabricated structures has been measured and considered in the simulation models. The results demonstrate the reliability of the fabrication as well as the robustness of the designed structures against tolerances in the fabrication process.