Interconnection Costs of Various Substrates-The Myth of Cheap Wire

Silicon has always been considered a dense and cheap medium for making wires, especially when compared with traditional interconnection media on a per interconnection basis. However interconnection costs in all technologies are essentially invariant on a per unit length basis. The advancing scale of integration has allowed active devices to be smaller and closer together, so wiring, both on chip and in systems, has been cheaper because there has been less of it. It is shown that substrate interconnection capability (in inches of wire per square inch of substrate) is the critical factor in achieving compact low-cost systems characterized by high interconnection density. A relationship between the active silicon area of devices on a substrate and the interconnection capability of the substrate is presented.