Substrate loss of on-chip transmission-lines with power/ground wires in lower layer

This paper discusses shielding effect of power/ground wires in lower layer. A conducting substrate affects characteristics of on-chip transmission line. However in many cases on actual chips, there are P/G wires between the signal wire and the substrate that may shield the substrate coupling. We show measurement and simulation results of on-chip transmission-lines with narrow yet many power/ground wires in a lower layer. Experimental results show that narrow power/ground wires in a lower layer in parallel to the signal wire, which are common in LSI power distribution network, shield substrate coupling and suppress substrate loss. On the other hand, orthogonal power/ground wires in a lower layer hardly mitigate substrate coupling.