The wordinterconnect (interconnection) in very large-scale integrated circuits
(VLSIs) means ametal lineoflow resistivity(high conductivity) which connects the
various electronic devices to carry current or to transport charge [1]. Theinterconnecting metal linesare separated from the substrate byinsulating layers(dielectric
material), except on the contact area. Since the creation of the integrated circuit
(IC) in 1960,aluminum(Al) or itsalloy(Al+Si+Cu) has become the primary material for interconnecting lines, andsilicon dioxide(SiO2) has become theinsulating
layer (dielectric material) to separate the interconnects. Besides being an insulating material for interconnecting lines, SiO2 has been used also as a gate material
in metal oxide semiconductor (MOS) devices. As a matter of fact, Al coupled with
SiO2has become the workhorse of IC technology.
Figure 1.1 shows a scanning electron microphotograph (SEM) of an integrated
circuit (IC) with local (which is used within a cell or a block using the finest pitch