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Copper-Interconnect-Feature

It's been 20 years since IBM first introduced copper interconnects in CMOS processing, sparking a small revolution in the procedure. Within a handful of years, both Intel and AMD had made the spring also, paving the way for reduced interconnect ability consumption and improved performance when compared with the older aluminum interconnect standard. Now, IBM believes there'southward enough life left in copper — and enough problems with graphene — that copper-based interconnects volition last until CMOS is itself replaced by something new.

EETimes spoke with IBM fellow Dan Edelstein at the IEEE Nanotechnology Symposium this week. Edelstein argues graphene is too difficult to manufacture, doesn't flow uniformly, and doesn't attain the same consistent performance equally modernistic copper interconnects. This is similar to problems we've heard scientists and researchers raise for years. Graphene is indisputably an amazing conductor, just if being adept at one thing was sufficient for integration into semiconductor product we'd all be walking around with 50GHz smartphones. No one has yet establish a cost-effective way of manufacturing graphite at scale or of manufacturing it to the tolerances required.

Copper vs. aluminum, interconnect and full delay

"Copper with a sparse cap of cobalt is better than graphene at carrying current and even at the smallest sizes imaginable copper interconnects are still the best solution, perhaps with cobalt, nickel, ruthenium or another platinum-grouping noble metals brought in to underlay it," Edelstein said.

EETimes' writeup on the slow advance of copper interconnects is an interesting look at how a technology that is considered commonplace today was difficult and challenging to bring to marketplace at the time. Copper offered pregnant benefits over aluminum, as shown in the prototype above, only it too required a tantalum-nitride sheath to act as a diffusion 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 only last one generation, but so far it has lasted 12,"Edelstein told EETimes. "And we believe that for CMOS it will last forever, except perhaps on the lesser layer next to the advanced node silicon transistors which may require cobalt, nickel, ruthenium or another platinum-grouping noble metals,"

Is Edelstein right? He may well exist, but not for good reasons. As semiconductor nodes accept become smaller, interconnect delay has risen and go an increasingly difficult problem to solve. It's part of the reason why CPU clocks haven't advanced much. We need a better interconnect solution, no question, merely so far, we simply haven't found one. The problems facing graphene are significantly more hard than the bug that made copper integration difficult in the 1990s, and until we can actually produce the stuff in the commercial volumes required for mainstream manufacturing, information technology wouldn't matter if information technology was the all-time interconnect material on Earth.

Copper, for improve or worse, is what we take to work with. Semiconductor manufacturers are going to have to find a way to make it work while living within its ever-growing limitations. There's been some work on graphene-coated copper, simply cipher has even approached prototype status, at least not yet.