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Graphene Transistors 10x Faster Than Silicon
Asadullah Ahmad writes "IBM has created transistors made from carbon atoms, which operate at 100 gigahertz, while using a manufacturing process that is compatible with current semiconductor fabrication. With silicon close to its physical limits, graphene seems like a viable replacement until quantum computing gets to desktop. Quoting: 'Researchers have previously made graphene transistors using laborious mechanical methods, for example by flaking off sheets of graphene from graphite; the fastest transistors made this way have reached speeds of up to 26 gigahertz. Transistors made using similar methods have not equaled these speeds.'" The other day we discussed what sounds like similar research by a group of scientists at Tohoku University; that team did not produce transistors, however.
To be honest I'm more interested in seeing proper 3D chips become reality. If you find some affordable way to produce chips with, say 10 000 layers, then processing power per volume unit would increase rapidly.
I think the major obstacle is going to be what to do about heat. The center of such a chip-stack would probably get quite hot so you probably want to run some form of liquid cooling through the chip itself. Alternatively materials like silicon carbide or diamond might be able to cope better with the high power density.
Graphene will probably be at least as important as a replacement for metallic interconnects as for transistors. Much of the area of a chip is covered by interconnects they are responsible for much of the heat and delay.
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My VLSI professor was in the forefront of the industry. He had some very good contract with some good R&D firms. One day, he told us that copper might one day replace aluminum as wires in chips. The lower resistance would make a big difference, but nobody had overcome the increased reactance yet. The next day, IBM announced that they had figured it all out. A year later, copper interconnect was being used in chips, and 6 months later, in iBooks. The same professor in a subsequent class was discussing SOI with similar promises of improvements, and similar "nobody has it figured out yet". A few weeks later, IBM came through again with an announcement. 2 years later, there it was in products.
With game changers like SOI and copper, IBM has gone to market in much less than 5 years.
As a former circuit designer, and still a CPU engineer, I can say without hesitation that I don't care about graphene. The transistors aren't the big factor anymore. Sure, smaller transistors are good to increase transistors per die, and reduce the distance between them, but wire RC delay is the big deal. Even if the Ioff goes down and Ion goes up, the speed of the chip isn't going to change much.
Things aren't going to get much better than copper -- it's very good already. Even if they upgraded to slightly lower resistance silver (and talk about a reactive metal!), the delay wouldn't change much. Lower K dielectric would help too. There are some minor improvements that can be done, but we're probably talking 5% here and there, and they probably don't add up to 20%.
Architecture changes are going to be important, from instruction optimization to multiple cores. The automated synthesis tools available also have an amazing amount of potential improvement -- placement and routing is a field with a lot of graph theory headroom. There is a world of difference still between "good enough" synthesis and what can be done by a well trained technician.