Ultrawideband Signal Transition Using Quasi-Coaxial Through-Silicon-Via (TSV) for mm-Wave IC Packaging

In this letter, a quasi-coaxial through-silicon-via (TSV) is presented for millimeter-wave integrated circuit (IC) packaging. The quasi-coaxial-via (Q-COV) structure in which one side ground metal is removed can minimize the interconnect length when it is mounted, in comparison to the coaxial-via (COV) structure. Simulation analysis shows that the Q-COV has similar electrical characteristics as the COV up to 100 GHz even though there is no GND on one side. To make the small signal core of the Q-COV, the silicon-core metallization process was used and a Si-interposer with Q-COVs of 50- $\mu \text{m}$ core diameter was fabricated and mounted on the glass board for signal transition analysis. The measured transition loss in the mounted Si-interposer was very small, only about 0.6 dB at 100 GHz, and the return loss was more than 20 dB for the entire measured frequency band (0–110 GHz).