Flip-Chip Approach for 500 GHz Broadband Interconnects

This paper presents the design and characterization of a broadband transition in the range dc to 500 GHz using the flip-chip concept. The extremely wideband performance is attained by optimizations in both process technology and electromagnetic design. On the process technology side, a thin-film process with scaled dimensions of 10 $\mu \text{m}$ for via diameter and 2 $\mu \text{m}$ bump height is employed for the chip and the carrier substrate. On the electromagnetic side, in addition to impedance matching, a detailed analysis of parasitic modes is considered for the design. The measurement results show less than 0.9-dB insertion loss per transition at 500 GHz and reflections below −18 dB over the entire dc to 500 GHz band.