Nanotube Transistors

orn writes: "Reuters is reporting that IBM has made a step toward using carbon nanotubes as the next best thing since sliced silicon wafers. They created a process that could potentially be turned into a manufacturing method to make extremely small transistors. Yahoo has a copy of the article. We all know that small transistors means higher speeds! Yum!" The NY Times has another article about the same technology, which we've mentioned before.

Comments

Enough speed. Where are massively parallel CPUs?!

[Anonymous Coward]

Give up this quest for ever smaller and faster single CPUs. We are just about at a dead end with this tech.

Where are the massively parallel machines? And I'm not talking about piddly 2/4/8 way or even 64 way SMP machines. I'm talking thousands to millions of independent CPUs all fitting inside a desktop sized PC.

Speed isn't the end all answer to computing. Look at the human brain and how insanely slow large ion synapses are yet look what the brain can do. It's not the speed. It's the parallelism.

Re:Mass Producability.

[Anonymous Coward]

Your understanding is basically correct - buckballs and carbon nanotubes are generated in what amounts to a low pressure carbon arc plasma. This helps to prevent normal chemistry from interfering and pulling out carbons before it is "too late" and a stable structure has been produced.

However, this doesn't require that the transistors be individually manufactured. Many molecules are produced in the plasma, and the next step of the work is to separate out the ones that are desired.

Right now the hard part of the process is moving the molecule into the right place to make the transistor. That is what, so far, must be done individually. However, ataching a type of molecule to a particular place is not something that must necessarily be done by hand. If you think about it, lithography is all about getting the etchant (or modern equivalent) to deliver itself to the right place. Also, recent 'designer' medicines have useful properties of self-delivery. So although this is a tricky problem, there is every reason to believe the engineers will find a solution.

-posting anonymously due to unjustified "bitchslap" thanks to the fascist editors

Re:Mass Producability.

[grub]

"My understanding of the process is that the nanotubes form in very hot furnaces by passing lasers and high current electric arcs through the carbon vapour in the furnace. This is not an easy process, and essentially requires that these transistors are individually manufactured. "

Certainly right now it's cost ineffective to make large batches of these, the article says as much. Remember though that the first transistors were hand soldered devices..

It's just a matter of time.

Re:Faster transistors won't help too much

[wass]

Transistors and the interconnection between them are three dimensional constructs. All of the dimensions have scaled downwards thought not all at the same rate. There are a number of things that impact real world circuit performance as a result of this. Wire for instance has a smaller cross section, the resistance of a wire is inversely proportional to this cross section (think of how water flows through a straw v.s how water flows through a garden hose). The capacitance is inversely proportional to its distance from ground, and this distance has shrunk.

One of the largest factors inhibiting speed of microelectronics is parasitic reactances (inductive and capacative), which you've casually mentioned, but not fully.

Every length of wire has some finite inductance, and the longer the wire, the more inductance it has. This is one of the hardest parasitic effects to kill. To see how this limits speed, picture how an inductor works. It basically stores energy in a magnetic field around itself, dependent on the current through the device. Magnetic fields don't like to change instantly, and when the current does change too quickly, it takes time for hte magnetic field to collapse (or create). This causes these parasitic inductances to act as virtual low-pass filters all over the circuit. Thus large inductances prevent one from quickly-changing currents, which limits quickly-changing voltages, which ultimately limits quickly-changing logic states of the device.

This is only talked about self-inductance, this inductance really depends on the location of all components in the circuit, as their magnetic fields all interact and they'll exhibit mutual inductances too.

The other reactive effect is parasitic capacitance, in which an electric field is created between varying components, usually between circuit-board traces and ground-planes, or between layers within the lithographed silicon devices. You mention capacitance, but the largest effect comes from the surface-area in common, not just the distance between traces. These parasitic capacitances don't like it when the electric field between them changes too quickly, so they also act as virtual low-pass filters all over the place, and also limit quickly-changing voltages. Ie, with a single-pole low-pass filter, it takes time for the voltage to ramp up, which means to ramp up to the threshold for a high/low transition will be limited.

Sometimes, the parasitic inductances and capacitances work together in nasty ways that they cause oscillations (or ringing), which is a real pain in the butt to try to kill off.

This is probably the primary reason the engineers want to shrink circuits - to kill the parasitics. That's why lead lengths are as short as possible and as narrow as possible on boards.

I always hear of overclocker enthusiasts talk about cooling their CPU's to lower and lower temperatures as if they can find no limit to their clock speeds. But they don't seem to acknowledge these inherent low-pass filters all over the place in terms of the parasitics.
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Re:Faster transistors won't help too much

[Alpha State]

Which is the biggest reason why the description, at least, is inaccurate. Faster transistors can help to a point - but by making the entire chip die smaller, and reducing the distance between the logic gates - that is where the speed gain is to be found.

Which is one reason why smaller == faster. Smaller transistors means less distance between them, which means shorter signal paths.

The other big factor is the energy involved in switching the transformer, which must be dispersed as heat. Smaller transistors also means less capacitance (or less charge to alter the state of the transistor), which means less current and less waste heat.

Unfortunately, these devices are getting to the point where they are triggered by only a few electrons, which means they will be easily affected by thermal noise. This will make designing a processor extremely difficult.

Faster transistors won't help too much

[sl3xd]

Unfortunately, we're getting to the point that the actual speed of the transistor/gates is nearing the speed of the traces between the different gates. Simply having faster transistors won't help bring faster computers.

We've begun to reach the point where the distance between the gates is the limiting factor; the amount of time it takes a signal to traverse the distance between gates being the critical part.

Which is the biggest reason why the description, at least, is inaccurate. Faster transistors can help to a point - but by making the entire chip die smaller, and reducing the distance between the logic gates - that is where the speed gain is to be found.

Re:Faster transistors won't help too much

[eXtro]

Most speed improvement is through architectural techniques and not smaller transistor size. Smaller transistors might enable the improvements since you can put more in a given area, but by and large a smaller feature size at this point in the game doesn't win much, if any speed.

Transistors and the interconnection between them are three dimensional constructs. All of the dimensions have scaled downwards thought not all at the same rate. There are a number of things that impact real world circuit performance as a result of this. Wire for instance has a smaller cross section, the resistance of a wire is inversely proportional to this cross section (think of how water flows through a straw v.s how water flows through a garden hose). The capacitance is inversely proportional to its distance from ground, and this distance has shrunk. It's also proportional to the surface area which would tend to lower the capacitance. The neighbouring wires are also closer however, which is more capacitance. What this means is that signals are travelling over a highly resistive capacitive network. Making sharp transitions (required for 'fast' digital circuits) is very difficult, sort of like trying to shake a skipping rope and making a square wave.

The transistor itself is smaller, but again the capacitance isn't necessarily decreasing but the ability of the transistor to drive current is. The current required from a transistor is proportional to the transition rate of the signals. Since we're trying to run faster we need more current, but our devices are physically smaller. This is why in high speed circuits, such as in the front side bus on the PIII or PIV, you'll typically see very large transistors and much wider wire.

There are other effects as well, such as higher electric fields in the drain and source of the transistor. There is a voltage difference between drain or source of the transistor and the body, since this difference is happening over less 'distance' the electric field is much stronger. This is why voltages keep dropping (which in turn makes the gain harder to get too!)

Sorry if this is a bit of a ramble.

Tiny little tubes?!

[micromoog]

I thought the whole point of transistors was to get away from tubes! And isn't it going to be a pain to find and replace those tiny little tubes when they burn out?

More background on carbon nanotubes

[hillct]

Fore more deep background check out the Nanotube website at: http://www.pa.msu.edu/cmp/csc/nanotube.html


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Re:Gordon Moore Speaks!

[Fatal0E]

"Intel has technical operations in China, Russia, India and so forth, and we have them there frankly to a significant extent because that's where there are trained people." (See! It has nothing to do with money!)

I'll do my best to not flame you but come on, use your head. Even if the amount of technically competent people were the same here (in the US) as in India, China, Russia and so forth they'd STILL have all those plants and research centers abroad.

It's all about the money cause they don't have to pay as much in those places. Take GM or whoever it was that moved a whole car manufacturing plant to Mexico. Are American plant workers any more skilled at manning a production line then their Mexican counterparts (after being trained)? In Intels case, I'm sure there aren't as many American engineers as Russia, China, etc but you have to admit saying it's not about the money (esp in Intel's case) is kinda ridiculous.

Insightful extracts from Cnet

[ishrat]

Nanotechnology would allow materials to be produced on a very small scale but in much higher volumes and at lower costs than traditional materials and manufacturing processes.

"It will take several years and additional breakthroughs before nanochips become as prevalent as silicon chips are today," said Harvard Professor Charles Lieber.

A possible shortcut, Lieber said, is the development of hybrid silicon-nanotechnology chips. Hybrid chips could be ready in about five years, he said, while pure nanochips will likely come within a decade.

Hybrid chips would be extremely dense, allowing substantial gains in processor speeds or the amount of data a memory chip can hold.

Looks like a substantial achievement from all this.

Size, not speed.

[Bonker]

Wasn't there an article just yesterday about a new litho technology that allowed chipmakers to etch on the molocule-size scale?

Faster transistors may give you a few more FpS in the FPS of your choice (I made a funny!) but Nanotube-transistors have a much greater application than speeding up existing technology. This kind of logic device can be used in small and nano-sized robots, increasing the range of tasks they can do and making them more controllable.

Ultimately, this is going to be the kind of advance we site as making the artery-scraper nanites and nerve-tissue replacements possible. Don't limit yourselves to thinking *solely* about data processing when new logic devices come along.

Mass Producability.

[gus goose]

My understanding of the process is that the nanotubes form in very hot furnaces by passing lasers and high current electric arcs through the carbon vapour in the furnace. This is not an easy process, and essentially requires that these transistors are individually manufactured.

This is by no means a commertially viable process.... yet. Don't hold your breath.

IBM's got the release out on this one

[Si_Druid]

Check out:
Chip Evolution: IBM Scientists Develop Breakthrough Transistor Technology with Carbon Nanotubes

They've got more dirt on this at
http://www.research.ibm.com/nanoscience/
http://www.research.ibm.com/atomic/

The Register's got it too...
http://www.theregister.co.uk/content/3/18556.html

Cool stuff.
Si.

IBM's Carbon Nanotubes

[science geek]

This is way cool. More deep science stuff about nanotubes is at the homepages at http://www.research.ibm.com/nanoscience/nanotubes. html and http://www.research.ibm.com/nanoscience/index1.htm l Can I get these with filters?