When are substrate effects important for on-chip interconnects?

In this paper, we investigate the effects of floating and grounded substrates with different conductivities of 100 S/m (medium) and 10.000 S/m (high) on on-chip interconnections in the frequency range from 1 Hz up to 40 GHz. We show that the frequency dependency of line parameters, especially the inductance and resistance per unit length, depends strongly on whether the substrate is grounded or floating, on the relative position of the ground line with respect to the signal lines, and on the substrate conductivity.