Full-wave characterization of high-frequency nonplanar interconnects.

Abstract

As monolithic and VLSI circuits are designed to perform multiple functions at heightened frequencies, increased complexity through the use of nonplanar interconnects is inevitable. These interconnects include strip-ridge structures, which consist of conducting strips suspended by dielectric ridges and/or a substrate above a ground plane in the proximity of other conductors on other ridges and localized superstrates, and monolithic dielectric waveguides, which are dielectric strips either raised above or embedded in a substrate. General methods for the analysis and design of nonplanar interconnects decrease the need for empirical characterization, resulting in substantial reductions in fabrication costs and design cycle time. A hybrid full-wave integral equation-mode matching (IEMM) technique is developed to study strip-ridge structures in the frequency and time domains, and a mode matching method is used to characterize monolithic dielectric waveguides. The IEMM technique analytically decouples a structure into two parts, namely, the conducting strips and the supporting dielectrics, and is thus capable of efficiently analyzing a class of three-dimensional structures in which the uniformity of the dielectric support structure along the longitudinal direction is preserved. Coupled microstrip on ridges, coupled microstrip with an etched groove, microstrip with finite substrate and ground plane, coupled multilevel microstrip with a finite intermediate dielectric layer, and an electro-optic modulator structure with an etched groove are characterized. The results introduce new methods for increasing packing density, decreasing crosstalk, and enhancing coupling in VLSI, monolithic and hybrid applications. Low-loss monolithic sub-millimeter-wave and terahertz dielectric waveguides are proposed and characterized. Examples for the 0.3-2.0 THz and 0.1-0.3 THz ranges demonstrate that the materials and structures available in monolithic technology allow the propagating power to be confined in a convenient region at a given frequency. A shielded transition from the waveguide to a power source is characterized from IEMM results. The presence of higher order modes due to the shielding is considered, and the electrical performance of a wide-band, efficient transition is presented.