Following the US Semiconductor Manufacturing Technology consortium Sematech’s announcement earlier this month that it had managed to produce silicon wafers using copper instead of aluminum transmission (CI No 3,236), IBM Corp looks like being the first of Sematech’s member companies to start making chips in this way. The industry has been working on using copper, which does not have the limitations of aluminum and should enable faster data transmission while coping with more transistors on smaller geometries, for some time now. The problem with copper is it can contaminate the silicon. IBM claims to have used a patented ‘fusion barrier’ to prevent the metal from poisoning the silicon, effectively an insulator. It is currently making the copper-based chips on a pilot manufacturing line in Fishkill, New York, but plans to move to high volume production out of Burlington, Vermont within a few months. IBM’s new process, which it calls CMOS 7S is an 0.12 micron design, which should enable it to create mainframe processors and PowerPC chips for use in its AS/400 and RS/6000 systems as well as Apple Computer Inc systems, with as many as 12 million gates, or between 150 million and 200 million transistors. They’ll be up to 40% more powerful than existing parts, be 20% to 30% cheaper to produce and operate using just 1.8 volts of power. With commercial ships of processors built using the design expected by the middle of next year, IBM’s way ahead of rivals such as Intel Corp, which doesn’t plan to start selling copper chips until 2002, although it is working on other new lithographic techniques to shrink its designs. Like IBM’s current 0.25 micron CMOS 6X PowerPC manufacturing process, CMOS 7S uses six layers of metal.
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