Double-Shielded Interposer With Highly Doped Layers for High-Speed Signal Propagation

In this paper, we propose a novel double-shielded interposer design with two metal layers directly contacting to the silicon substrate surfaces for high-speed signal propagating along through silicon vias (TSVs). To enhance the shielding effects, shallow highly doped silicon is made on both sides of the silicon interposer forming ohmic contact between the metallization layer and silicon. The metallization layer is etched into meshed pattern to prevent delamination. Based on the imaging method, we derive the equivalent circuit model of the proposed double-shielded interposer, and the accuracy and efficiency of the equivalent circuit model is verified by full-wave method. The proposed design can concentrate the electromagnetic field around TSVs, so that it has a lower insertion loss than the conventional ground-signal (GS) structure without shielding. This is especially useful when the low-resistivity silicon is used for the interposer. Finally, some applied guidelines are proposed to strengthen the performance and simplify the silicon fabrication processes.