Manufacturable Low-Cost Flip-Chip Mounting Technology for 300–500-GHz Assemblies

We developed a chip mounting technology suitable for low-cost assemblies in the 300–500-GHz frequency range, compatible with standard chip and submount fabrication techniques. The waveguide and transition designs are compatible with indium phosphide heterobipolar transistor millimeter-wave monolithic integrated circuit chip architecture. Increased conductor shielding in different multilayer thin-film waveguide topologies is applied to suppress radiative losses, enabling low-loss interconnects up to 500-GHz bandwidth. Standard flip-chip align-and-place equipment is used to assemble the chips onto submounts. Losses are evaluated by banded ${S}$ -parameter measurements between 10 MHz and 500 GHz. For an optimized stripline-to-stripline transition, an insertion loss of less than 1 dB was measured at 500 GHz.