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Copper-Interconnect-Feature

It'due south been xx years since IBM get-go introduced copper interconnects in CMOS processing, sparking a minor revolution in the process. Within a handful of years, both Intel and AMD had fabricated the spring as well, paving the style for reduced interconnect power consumption and improved performance when compared with the older aluminum interconnect standard. Now, IBM believes there's enough life left in copper — and plenty problems with graphene — that copper-based interconnects will last until CMOS is itself replaced past something new.

EETimes spoke with IBM fellow Dan Edelstein at the IEEE Nanotechnology Symposium this week. Edelstein argues graphene is too hard to manufacture, doesn't flow uniformly, and doesn't achieve the same consequent performance as mod copper interconnects. This is similar to bug we've heard scientists and researchers raise for years. Graphene is indisputably an astonishing usher, merely if beingness skillful at i thing was sufficient for integration into semiconductor product we'd all be walking around with 50GHz smartphones. No ane has withal found a cost-effective style of manufacturing graphite at scale or of manufacturing it to the tolerances required.

Copper vs. aluminum, interconnect and total delay

"Copper with a thin cap of cobalt is amend than graphene at carrying current and even at the smallest sizes imaginable copper interconnects are still the all-time solution, maybe with cobalt, nickel, ruthenium or another platinum-group noble metals brought in to underlay information technology," Edelstein said.

EETimes' writeup on the tiresome advance of copper interconnects is an interesting look at how a technology that is considered commonplace today was hard and challenging to bring to market place at the time. Copper offered pregnant benefits over aluminum, as shown in the image higher up, simply information technology likewise required a tantalum-nitride sheath to human activity every bit a improvidence barrier between copper ions and the silicon itself. IBM had to develop entirely new methods of connecting the various layers of the CPU; the techniques that had worked well for aluminum did not function for copper.

"At first our competitors said that it would simply final one generation, but and then far it has lasted 12,"Edelstein told EETimes. "And nosotros believe that for CMOS it volition concluding forever, except maybe on the lesser layer adjacent to the advanced node silicon transistors which may crave cobalt, nickel, ruthenium or some other platinum-group noble metals,"

Is Edelstein right? He may well be, simply not for good reasons. Every bit semiconductor nodes take become smaller, interconnect delay has risen and go an increasingly hard problem to solve. Information technology's part of the reason why CPU clocks oasis't advanced much. We need a better interconnect solution, no question, but and then far, nosotros simply haven't found 1. The problems facing graphene are significantly more than difficult than the issues that made copper integration hard in the 1990s, and until we tin can actually produce the stuff in the commercial volumes required for mainstream manufacturing, information technology wouldn't matter if it was the best interconnect material on Earth.

Copper, for better or worse, is what we have to work with. Semiconductor manufacturers are going to have to find a mode to get in work while living within its ever-growing limitations. In that location's been some work on graphene-coated copper, but zippo has even approached image condition, at least non withal.