Electrical fuses help IBM chips heal themselves

IBM's has claimed its eFuse technology brings it closer to autonomic computing by allowing chips to sense their own flaws and...

IBM's has claimed its eFuse technology brings it closer to autonomic computing by allowing chips to sense their own flaws and reconfigure themselves without outside intervention.

The eFuse technology replaces laser fuses, used to heal chips while they are still in the fabrication process, with electrical fuses that can reroute traffic around inactive or poorly functioning areas on a chip, said Subramanian Iyer, a senior IBM engineer .

Most chip manufacturers use laser fuses that are activated during the testing phase of the manufacturing process before individual chips are cut from a wafer. A testing engine built into the chip detects any faults incurred during the manufacturing process and shares that information with an outside technician who then blows the fuses, redirecting traffic around the bad sector of the chip.

These testing engines have never been very sophisticated because they were not used after those tests, Iyer said. The combination of electrical fuses and a more sophisticated built-in testing engine raises the bar for self-healing technology on chips.

The technique draws on a principle called electromigration. Electromigration used to be a dirty word in the chip industry. It refers to the tendency for a large amount of electric current to cause structures inside chips to fail, allowing that current to escape the chip and literally melt the processor.

But fuses are designed to break when a large electrical current passes through them. The tricky part is making sure that electrical current passes into the fuse only, and not the rest of the chip, but IBM has resolved that issue, Iyer said in a technique that has been patented.

When the on-chip testing engine senses a fault, it can direct the electrical fuses to activate and shift signals away from the malfunctioning transistors. This helps to make the chip more efficient, and the process can occur many times during the life of the chip as workloads change, Iyer said.

Another benefit of electrical fuses is that the structures can scale in the same proportions as the rest of the chip, Iyer said. Laser fuses did not decrease in size when chip makers moved to a new process technology, but electrical fuses can decrease in size as chips continue to shrink, he said.

IBM plans use the eFuse technology in all of its chips as it moves to 90-nanometer process technology, including the Power5 and PowerPC 970FX chips that are already available, Iyer said.

Tom Krazit writes for IDG News Service


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