Current distribution and internal impedance of interconnect

A novel volume integral equation for the current distribution over interconnects with arbitrary cross-sectional geometry is presented based on the free space Green´s function without approximation. For very low frequency, it can be reduced to the widely-used quasi-static approximation. The quasi-static volume integral equation is not accurate enough for the calculation of current distribution. A comparison is made with the different methods known in literature to calculate the per unit length internal impedance. Detailed discussion is given for the different current distributions and the definitions with their effects to the internal impedance, either for a high frequency range or a low frequency range.