Low Loss, Cu damascene interconnects and passives compatible with GaN MMIC

We report a Cu damascene process on multi-layer benzocyclobutene (BCB) dielectrics compatible with GaN MMICs that enables the creation of low-loss, high power handling and high current carrying interconnects. The reported process uses two thick Cu traces (7 μm and 3 μm) and two supplemental Au layers. 7 μm thick Cu traces with width and pitch of 4 μm were realized. Reported circuits showed 0.11 dB/mm loss at 50 GHz, inductor Q-factors of 30 and 57, 3:1 planar balun with less than 2 dB insertion loss, 100% yielding RF and DC via chains.