Through-interposer grounding using blind vias

Abstract

A current path is provided through an interposer to ground a grounding pattern associated with a transmission line, by exploiting an interposer substrate that has a high-resistivity portion at a first surface and a low-resistivity portion extending from the high-resistivity portion to a second surface of the interposer. Moreover, a set of blind via-holes comprising electrically-conductive material extend from the first surface of the interposer substrate through the high-resistivity portion and into the low-resistivity portion. Top-to-bottom connection can be made using the conductive material in the blind vias and using the low-resistivity portion of the substrate, while the high-resistivity portion of the substrate impedes current leakage from the transmission line to the second surface of the substrate. The number and dimensions of the blind via-holes control the impedance of the grounding pattern relative to the transmission line's characteristic impedance.