Transmission line models for high-speed conventional interconnects and metallic carbon nanotube interconnects

The transmission line is a powerful model to describe in a simple and accurate way the propagation of electric signals along interconnects of different kind. The “standard” transmission line model is derived under a series of assumptions involving both the physical structures and the carried signals, which are satisfied for a large amount of cases of practical interest. Nowadays the signal speed is growing rapidly due to market requirements and to progress in technology. As the velocity of the electrical signals increases, high frequency effects due to dispersion and radiation losses, which the standard transmission line model is unable to describe, are no more negligible. In the future large scale integration electronics the interconnect cross-sections will become smaller and smaller down to nanometric dimensions. As interconnect sizes shrink copper resistivity increases due to grain and surface scattering effects and wires become more and more vulnerable to electro-migration due to the higher current densities that must be carried. In order to overcome these limitations the use of metallic carbon nanotube as interconnects has been proposed and discussed recently. Here both an “enhanced” transmission line model able to describe the high-frequency effects due to dispersion and radiation losses in conventional high speed interconnects and a new transmission line model for metallic carbon nanotube interconnects are reviewed. Some applications to interconnects of particular interest in present high-speed electronics and in future nanoelectronics are presented