Simulation and modeling of mode conversion at vias in multilayer interconnections

The process of signal flow at vias in multilayer interconnections is discussed as a general phenomenon involving partial conversion of signal-line waveguide mode energy into parallel-plate waveguide mode energy. This partial conversion of linearly propagating mode into a cylindrically propagating parallel-plate waveguide mode at vias is discussed and illustrated with the graphic results of a 3D, full-wave propagation analysis. Based on these observations, equivalent circuits of vias which incorporate the mode conversion phenomenon are proposed. The effectiveness of the proposed model is demonstrated as a comparison between the 3D, full-wave simulation and SPICE circuit simulation.