A method for modeling the impact of conductor surface roughness on waveguiding properties of interconnects

A methodology is proposed for accounting for the impact of random conductor surface roughness in the electromagnetic analysis of the propagation characteristics of high-speed interconnects. The proposed methodology replaces the rough-surface conductor cross-section with a compound one, where a thin outer layer, conforming to the conductor contour and of frequency-dependent thickness and conductivity is used in place of the surface roughness. The resulting compound conductor model facilitates extraction of the waveguiding properties of the interconnect using electromagnetic field solvers. The attributes of the method are demonstrated through the electromagnetic analysis of a microstrip transmission line structure and through correlations with measurement data.