Closely Packed Microstrip Lines as Very High Speed Chip-to-Chip Interconnects

As the density, complexity, and speed of VLSI circuits continue to increase, it has become apparent that the chip-to-chip interconnections can limit overall performance of an integrated system. Here the analysis is discussed of interconnections as long transmission lines whose cross-sectional dimensions are the order of several micrometers. The relevant parameters are signal delay, loss, crosstalk, and spatial density. The time domain response of coupled microscopic transmission lines is also shown. Preliminary results indicate that conventional quasi-TEM analysis is inadequate but that modification can bring about substantial improvement. A proposed two-level structure appears to offer an attractive combination of high-speed (c/1.8), low crosstalk (less than ten percent over 10 cm), low loss (0.05 dB/mm at 1 GHz), and high density (35/µm period) and can operate at frequencies exceeding 1 GHz.