Discontinuities in very high-speed lossy transmission lines for chip-to-chip interconnections

As the speed of VLSI circuits continues to increase, the performance of integrated systems is limited by chip-to-chip communications. We have already reported that a high density chip-to-chip interconnection scheme as shown can provide attractive transmission line characteristics up to frequencies as high as several gigahertz, Practical high-speed integrated systems, however, contain a variety of discontinuities in the strip conductor such as fan-outs, via holes between levels, and right-angled bends. In this paper we describe an analysis of signal reflection at these discontinuities based on three-dimentional, finite element method, solutions of Poisson´s and Maxwell´s equations, The results bear out qualitative predictions and lead to Suggested design rules for a fan-out structure.