Speed lift for chips

Copper circuitry for chips promises to boost performance

IBM plans to replace aluminium with copper in the electrical circuitry of a future generation of computer chips.

The announcement signals the development of faster, more powerful and efficient electronic goods and services for people who hanker after the latest gadgetry.

The breakthrough makes it possible to place, on a single chip slightly smaller than a postage stamp, the processing equivalent of 33 Pentium processors – each capable of performing the central processing functions of a powerful desktop computer.

Processing speeds of about 400MHz will be possible, as compared with the 200MHz benchmark of today’s high-end desktop PCs.

Coupled with the much faster information transfer rates available, this development means digital communications is set to grow exponentially. Long-awaited networking technologies such as asynchronous transfer mode (ATM) should become more widespread now that reliability and other hurdles can be tackled using the new chips. For a start, they run faster, but are less prone to overheating.

A spokesman for IBM Microsystems says: ‘There is a real hunger for performance, which is driven by the expansion of the Internet. But network infrastructures are still inadequate and problems of access are a common complaint.’

More immediately, electronic gadgets such as the Nokia Communicator -which combines a mobile phone with a miniature computer – will acquire the potential for many more useful functions. IBM’s copper-circuit technology means that the central processing functions of the existing space-guzzling printed circuit board can be executed by one chip.

Copper is about 35% better as an electrical conductor than aluminium, and second only to silver – the reason for copper’s use in wiring even when the metal is more expensive. The quantities used by the semiconductor industry are quite small, so a global switch to copper will have a minimal impact on suppliers.

That switch is unlikely to happen overnight. IBM took 10 years to come up with a viable solution for using copper, in the process spending a ‘significant’ part of its research and development budget, which topped $4bn in 1996. And main rival Intel has put its entry into copper fabrication as some time after the year 2000. Both companies have mastered volume production of 0.25 micron wafer size technology which they use in their high-end chips.

The demand for smaller, faster chips is driving the move to copper. IBM claims a clear market lead with a 0.20 micron chip, which it says is possible only through using copper.

IBM highlights the real benefit that highly conductive copper brings – the ability to pack more circuit components into a given space. The new chip can carry up to 200 million transistors compared with, say, five million on a Pentium chip. Such a chip either becomes very fast or can house a complete control system rather than just one part of it.

The big drawback to using copper in semiconductors is leaching, where the metal breaks down in the silicon oxide substrate during the ‘pressure-cooking’ process called chemical vapour deposition (CVD). This does not happen with aluminium. The breakdown contravenes the industry principle of ‘clean interconnect’, and leads to faulty chip operation.

IBM says the new process does not involve CVD and is relatively simple to set up in a wafer fabrication manufacturing environment. He describes it as a chemical bath, which provides a ‘superglue’ that both attaches the copper to, and protects it from, the silicon.

The process is one of several developed by IBM’s R&D division for IBM Microsystems, the patent-owner. The company is making aspects of the technology available to other chip-makers through Sematech, the US semiconductor research consortium.

Pilot production of the chips is under way at IBM’s Fishkill manufacturing plant in New York state, and high-volume production starts early next year at Burlington, Vermont.

IBM’s RS6000 server machines are the likely first customers for a microprocessor chip which could eventually replace the IBM-developed PowerPC 750 as the main processor in these high-end computers.

Ultimately, users of Apple computers that also run PowerPC processors could also benefit from much faster machines suited to multimedia and graphics.

The next step is a drive into the market for special-purpose chips called ASICs – these could be snapped up by the makers of, say, even tinier digital mobile phones.