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Intel: Metal in Future Chips = Less Leakage (updated)
securitas writes "Intel is contemplating using metal instead of silicon in future chips for the 'transistor gate, which controls whether a transistor is on or off' and the 'dielectric, an insulating layer below the gate,' which are respectively made of silicon atoms and silicon dioxide. 'Millions of minuscule switches that make up silicon chips leak electricity when they're supposed to be shut off. To compensate, engineers have increased the current, driving up power consumption, decreasing battery life for portable devices and generating more heat.' AMD has also experimented with metal instead of silicon. By moving to metal AMD and Intel expect to reduce electricity leakage. More from AP via SeattlePI and the Miami Herald." Update: 11/05 15:25 GMT by T : Read on below for some information from Intel on why this is a good thing.
gManZboy writes "Following up on the Intel news that about using metal in chips -- here's an explanation from Shekhar Borkar (Intel Research Fellow) about why heat, power, and sub-threshold leakage, not transistor size, are the real challenges to Moore's law. Apparently, in order to make chips much faster, we're going to have to pump more electricity in then anything else in our houses -- and they'll soon be as hot as a nuclear reactor -- no, really."
Man, and here I thought silicon felt weird.
In the AMD article the use of Nickel is mentioned.
I have no trouble understanding a switch from poly to metal for gate connections... but a metal dielectric? That seems to run counter to common sense. The dielectric is, by definition, required to be an insulator, whereas metals, also by definition, conduct electricity rather well. What is this magic substance?
:-)
I love this site sometimes - where else can you post completely clueless questions and be virtually guaranteed to get an intelligent response from at least two people with PhDs in semiconductor physics?
These sigs are more interesting tha
You are thinking of the Copper traces instead of Aluminium, the transistors remained Silicon. Here they are talking about metal transistors.
to MetalValley!
:)
Now, instead of "experiment in silico", it would be "in metal" (??) or "in Fe|Au|Cu"
DNA in your Linux: DNALinux
...diamonds?
I thought that the manufacture of diamonds was set, and only needed to step up its production. Gemesis has been making, for less than $100, gems that would be worth hundreds of thousands if naturally mined.
The most promising thing about these diamonds is that, being cheap, they open the door for cpu cooling. Diamonds are tolerant of exponentially higher temperatures than silicon, so why aren't we hearing about intel, amd, motorola, ibm, TI, and sgi taking advantage of this new technology.
Metal? What about metal is unprecedented? What about it has kept us from using it before? Diamonds are the future, not metal.
The history of Moore's Law.
Or if you are interested in Moore's original paper, you can find it here.
I want to drag this out as long as possible. Bring me my protractor.
The chemistry of the non-silica gate dielectric requires that the gate itself be non-silicon, and metals are better conductors anyway. (For larger transistors, we're already running into trouble from the distributed resistance of the gates.)
Hope that helps.
Lacking <sarcasm> tags,
I thought it was already established that silicon implants were prone to leakage.
But switching to metal? Man, I'd hate to walk outside on a cold Montana morning in February with those.
What's that? Silicone? They're not the same? Never mind. Carry on. Sorry.
So you're telling me SOI is NOT a busty gal in an angora sweater?
Interesting how IBM has discovered that moving to metal for processors and away from metal for hard drives. (Newest Hitachi/IBM notebook drives use Pixie dust which is actually glass. The platters in these hard drives are also ferro impregnated glass platters)
Yell & scream & rant & rave... it's no use... you need a shaaaave ~ Bugs Bunny
Why is VLIW not more popular? Because compiler technology isn't yet good enough and current VLIW designs have restrictions that get in the way of the best performance.
Over the years, there have been many attempts to use techniques such as VLIW, which sound great on paper, but don't do well in practice. What have worked the best, at least through the 90s, are architectures that do a lot of simple things fast.
You can make VLIW fast, Intel has managed that, but at great cost in both silicon and software.
Be careful when making generalizations about a processor line such as the P4 - there have been quite a few P4 generations, each better than the last. Latencies have gone down.
I think that parallelism (eg. HyperThreading, multicore, etc.) is where the real-world performance gains will come from. Single-threaded benchmarks don't accurately reflect realistic workloads.
My course in VLSI design was many, many years in the past, but what I do remember is that early integrated circuits used metal gates in the fabrication process. That process was later abandoned in favor of polysilicon because poly was much easier to work with at smaller feature sizes (I'm a bit foggy on this one). Gee, so now we're going back to metal gate processes, and we'll have real metal-oxide-semiconductor field effect transistors again?
If this is becoming easier to do at deep submicron level, I suppose processes for making deep submicron feature-sized Gallium-Arsenide MESFET's also got easier? Now wouldn't we just love to have such GaAs chips on our desktops... (I do know I'm forgetting another difficulty in working with GaAs, anyone care to remind me why GaAs is not as common as silicon today?)
Qu'on me donne six lignes écrites de la main du plus honnête homme, j'y trouverai de quoi le faire pendre.
No. The bonds between silicon atoms are covalent. A metal (e.g. copper) has a "cloud" of electrons free to move around in the lattice. Silicon is a semiconductor, with the charges bound to the atoms except when there's enough energy (typically thermal) to kick them loose.
Lacking <sarcasm> tags,
the materials for a capacitor's contacts have nothing to due with it's ability to store charge (thus its capacitance). it is only a function of the device's dimensions and its dielectric.
You are thinking of the Copper traces instead of Aluminium, the transistors remained Silicon. Here they are talking about metal transistors.
Not true at all. The copper in IBM's process is for interconnects, not traces. I'm not sure what metal they use for the traces, but it's probably aluminum and definitely not copper. The connection between layers (interconnect) are copper plugs.
The metal intel is talking about is strictly for the gate terminal connection of the transistor. The transistor is still doped silicon or gallium arsenide or whatever semiconductor they are using.
Nope, the traces are copper instead of aluminium here is an IBM article from 2000. Unless "wiring" and "traces" no longer mean the same thing.
I dont see any mention of the type of metal that would be most suitable. I'm sure all metals are n't created equal.
Actually, two types of metal are probably needed. One for nmos transistors and another for pmos transistors. Nmos and pmos transistors have different threshold voltages (the voltage at which the device turns on), but ideally you would like both types of transistors to switch at the same voltage. The threshold voltage of a device can be shifted by modifying the "workfunction" of the gate metal. The workfunction is the energy required to remove an electron from the metal surface.
One reason polysilicon gates are used in conventional CMOS is that the workfunction of polysilicon can be modified by changing the level of doping and the type of dopant material (usually B, P or As). Thus, polysilicon gates can be used for both nmos and pmos transistors and by varying the doping, both types of devices can have the same threshold voltage.
Shifting the workfunctions of metals, using dopants is not so straightforward. As a result it will probably be necessary to use two different metals having different workfunctions for nmos and pmos transistors. Further complicating matters is the fact that the gate metal can interact with the dielectric material, modifying the effective workfunction and thus the threshold voltage. So, while the isolated metal may have the necessary workfunction, the workfunction may shift when the metal is part of a device. Thus, a lot of testing and experimentation is needed to find a metal that has the proper workfunction after it has been put into a device.