Getting Around Aluminum
Inside microprocessors are millions of tiny switches, or transistors. When turned on or off, these switches carry instructions for computers and other electronic devices. Making the switches smaller and more numerous boosts performance, but increases the difficulty of wiring them together. The semiconductor industry has used aluminum wiring on chips for over 30 years. But the ever-shrinking universe of semiconductors has made aluminum more and more problematic, since it resists the flow of electricity as wires are made ever thinner and narrower.
Copper Is The Answer
After nearly 15 years of research, IBM scientists announced in September 1997 a new advance in semiconductor process that entails replacing aluminum with copper. Copper has less "resistance" than aluminum, and therefore transmits electrical signals faster. However, it doesn't mix as well with silicon, the base material of semiconductor chips. The IBM researchers found a way to put a microscopic barrier between the copper and silicon in a way that actually reduced the number of steps needed to complete a chip.
With this development, IBM is able to produce extremely intricate circuit designs with copper at widths of 0.20 microns -- down from the current industry standard of 0.25 microns. A micron is 1 millionth of a meter; one-fourth of a micron is hundreds of times thinner than a human hair.