Graphene Transistors 10x Faster Than Silicon 170
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.
3D chips (Score:5, Interesting)
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.
Interconnects (Score:4, Interesting)
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.
Re:3D chips (Score:3, Interesting)
3D chip manufacturing would be interesting. As well as having a possible stepping stone towards universal fabrication, you would also have a great increase in the potential number of connections between processing elements. Connectivity is one of the main divides between silicon and neural tissue, so this may have implications for artificial intelligence. Two singularities for the price of one!
Re:Didn't Produce Transistors? Oh Come On! (Score:3, Interesting)
Hard drives would be a more interesting example. There is an industry that keeps changing the maximum, from new perpendicular storage now to using heating lasers to increase data density. Barriers keep getting broken on what is essentially the same old media. However once the slow speeds of holographic storage are solved, there is no doubt that 3D storage will overtake magnetic-based media. These sorts of sea changes are brought about by thresholds. Until these concepts graduate from prototype to production AND cost so ridiculously less per ghz than existing tech, it'll be silicon for the foreseeable future.
Re:Didn't Produce Transistors? Oh Come On! (Score:3, Interesting)
I never mentioned the 56k limit. I'm referring to the fact that the same signal is used but tweaked each generation to allow greater speeds in ways that weren't even considered. For instance, from 300 baud modems to 56K modems. Frequency shifts, phase shifting, duplexing, echo cancellation, QAM, etc. All of these pieces allowed more data to be sent over the same old twisted pair in ways they never thought possible.
All of those advances were evolutionary rather than revolutionary, and they benefited all sorts of communication mediums in use today. Had we just stumbled on the next big thing without taking that path, we would have lost the benefits of struggling at the limits of that particular technology.
Re:hold yer horses (Score:1, Interesting)
I agree. According to the Science article, "No clear current saturation was observed at drain biases up to 2V or before device breakdown." The basic "transistor" nature of a device dictates it must have both a linear AND saturation region for switching applications.
Re:How long until you can buy it? (Score:4, Interesting)
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.
Silicon is still faster (Score:3, Interesting)
Graphene is still very much a lab technology which isn't anywhere near ready for commercial production of devices. It may turn out to replace Silicon one day, but guess what, people keep doing amazing shit with silicon because it's still the cheapest material system for fabrication.
Apologies to those without IEEE access, but here is a paper discussing a recent 150GHz Silicon CMOS amplifier: A 1.1V 150GHz amplifier with 8dB gain and +6dBm saturated output power in standard digital 65nm CMOS using dummy-prefilled microstrip lines [ieee.org]. That's pretty awesome in my book. It's pushing the amplifier very close to fmax of the actual transistors, but it works and it's in a commercial silicon process.
There are always applications where we can do better systems with more expensive materials like GaAs, GaN, InP, Graphene, etc... but silicon is cheap and easily mass-produced, so lots of engineers work on pushing it to incredible performance.