Copper

• The discovery of copper dates from prehistoric times. There are reports of copper beads dating back to 9000 BCE found in Iraq. Methods for refining copper from its ores were discovered around 5000 BCE and approximately 1000 years later it was being used in pottery in North Africa. Part of the reason for it being used so early is simply that it is relatively easy to shape. However it is somewhat too soft for many tools and around 5000 years ago it was discovered that when copper is mixed with other metals the resulting alloys are harder than copper itself. As examples, brass is a mixture of copper and zinc while bronze is a mixture of copper and tin.
• Copper has made possible the continued, efficient development of the electrical industry because it has the highest conductivity of the commercial metals. From high voltage transmission cables to microcircuits, and from megawatt generators to computers, copper is the metal of choice in many aspects of electricity generation, transmission, and use.

• The electrical industry is the largest user of copper, but it is also used in coinage, tubing, water purification, and other applications.
• Copper Wire: Copper, having a high conductivity, is used extensively in wiring. Coils, chokes and VDU beam magnets are all made from enamelled high conductivity copper that is ductile enough to be wound in to slots, limp enough to stay in the slots and strong enough to stand the forces generated by electro-magnetism.
• Power Supplies: Motors and other power supplies are also a major application of metallic copper. For reliable operation of computers, power supplies must be protected from the harmonics generated by electronic equipment.
• Integrated Circuits: Microchips have leadframes made of copper alloys that are strong enough for the small pins to be forced in to the socket, hold their strength and springiness at operating temperatures, are good electrical conductors and can easily be gold plated for total corrosion resistance.

An innovative new application of copper is its extensive use in computer chips. IBM has developed a new semiconductor manufacturing process which uses copper instead of aluminum. Copper will allow IBM to shrink electronic circuitry to smaller dimensions and fit more computer components onto a single chip.

Chip designers have long sought to use copprer because of its high conductivity compared to aluminum. Copper's only drawback, up until now, was its tendency to diffuse into and damage the chip's silicon layer. IBM's new manufacturing process employs a barrier material which isolates the chemically vapour-deposited copper from the silicon.

The photograph at left (courtesy of IBM) shows a highly magnified Scanning Electron Microscope (SEM) view of IBM's first-to-market six level copper interconnect technology.

For more information about copper in computer chips, visit IBM's homepage: http://www.ibm.com