Interconnect mode conversion in high-speed VLSI circuits

A modification of the electromagnetic field configuration (mode conversion) at interconnect discontinuities in deep submicron digital ULSI circuits was investigated by using a full wave electromagnetic analysis. The mode conversion analysis is indispensable in identifying the signal return path, the return current distribution, and therefore for an accurate inductance modeling which remains a challenging problem. On the other hand, switching activity of a high speed CMOS circuit may produce large current derivatives. These transient currents can generate large potential surges and coupled noise due to the parasitic resistances and inductances of the wires. To this aim, we determined a simple design rule to reduce the mode conversion phenomenon and, therefore, decrease noise in high-speed ULSI circuits.