Artificial Dielectric Shields forIntegrated Transmission Lines

We present a novel shielding method for on-chip transmission lines built on conductive silicon substrates. The shield consists of an artificial dielectric with a very high in-plane dielectric constant, built from two patterned metal layers isolated by a very thin dielectric film. Inserted below an integrated coplanar transmission line, the artificial dielectric layer blocks the electric field of the line from entering the silicon substrate. Shielded coplanar waveguides fabricated on a conventional silicon wafer show a two- to three-fold loss reduction compared to unshielded lines at frequencies below 30 GHz.