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IBM and GlobalFoundries go Gate-Last for 20nm

IBM and GlobalFoundries go Gate-Last for 20nm

GlobalFoundries and IBM have bitten their lips and admitted that gate-last is indeed the way to go.

Despite their previous insistence that gate-first was the correct approach to manufacturing future CPUs - including upcoming 32nm/28nm models - GlobalFoundries and IBM have now changed their minds, announcing a gate-last strategy for the fabrication of their 20nm and 22nm chips.

The two major chip fabs follow behind Intel and TSMC, who have already committed to a gate-last approach for their advanced nodes. In fact, Intel has even championed the use of the gate-last technique for its entire high-k metal gate line-up since the introduction of its 45nm CPUs.

In case you're unfamiliar with the latest CPU manufacturing jargon, gate-last and gate-first refer to the point at which a transistor's gate is put onto a CPU-production wafer. Previously, CPU transistors featured a silicon gate and a silicon dioxide insulator.

However, in order to combat the problems with current leakage as silicon gets thinner, most fabrication firms have now been replaced the silicon-based parts with a metal gate and a high-k insulator made from a material such as Hafnium. This means that a fabrication company has to choose whether the metal gate electrode is dropped onto the wafer before or after the high-temperature heating process.

We questioned GlobalFoundries about this matter ourselves when we previously met the company late last year. However, an equally sceptical CPU guru, David Kanter of Real World Technologies, has now confirmed that the two companies announced the change in strategy during the recent Common Platform tech day, stating:

'The Common Platform members (mostly GF and IBM) had maintained that gate first had density advantages which overshadow the defectivity and performance benefits of gate last.

This always rung a bit hollow to me and did not seem very plausible. The two highest volume logic manufacturers (TSMC and Intel) clearly opted for gate last, which is a pretty strong signal. There were also rumors of Samsung and others pressuring IBM to move to gate last...so the writing has been on the wall for some time.'


Also, perhaps more worryingly, Kanter goes on to comment about the current state of the 32nm node that continues to use the gate-first technique:

'The 32nm ramp has not been going particularly well, and is further behind Intel than usual. There were whispers that this was at least in part due to the choice of a gate first process flow. In theory, removing the challenges associated with gate first should result in a faster and smoother ramp for IBM, GF, etc. and benefit AMD in terms of time to market for 20nm'.

Kanter also goes on to say that gate-last is superior, because it provides a better choice of transistors for higher performance, which could crudely translated into better overclocking potential, as well as lower leakage. We've yet to see how any GlobalFoundries 32nm device performs, as the company previously admitted that AMD's Llano is 'driving yield learning,' so we'll have to wait and see how it all works out in this year's Fusion parts.

Will Intel stretch its lead even further? Will AMD's Llano and Bulldozer CPUs suffer this year? Let us know your thoughts in the forums.

10 Comments

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mclean007 20th January 2011, 12:33 Quote
What does this mean in English?
arcticstoat 20th January 2011, 12:50 Quote
Quote:
Originally Posted by mclean007
What does this mean in English?

I've added a couple of paragraphs to the beginning to try to clarify this - gate-last or gate-first basically refers to the point when you put the metal gate onto the production wafer.
Snips 20th January 2011, 13:02 Quote
Hafnium? Did you just make that word up? is it like unobtainium used in that dances with smurf's filck by James Cameron?
Bindibadgi 20th January 2011, 13:10 Quote
Sorry I get ahead of myself sometimes :o

The 'Gate' is the transistor gates (NFET and PFET iirc). First vs Last means do you do the transistors before other chemical techniques, or after. Gate First is cheaper because it's quicker, but it causes yield and performance issues as the chemicals that get flushed over it on subsequent treatments also errode those nice transistors you've just put down. Gate Last is more costly and difficult as the transistor gate goes down AFTER most/all the treatments, not to mention giving more freedom for the choice of materials used on later PFET (again iirc), which ultimately rewards better yields and performance. For evidence of that look how well Intel's 45nm and 32nm hardware overclocks!

Intel's advantage is that it's costs are lower because it does everything itself, so it can optimise a longer process. However if you're GloFo or TSMC, you have to absorb the cost or your customers product probably becomes less or uncompetitive. It's particularly a problem for AMD, who has to compete with Intel, and usually does so on price.
jrs77 20th January 2011, 13:44 Quote
Quote:
Originally Posted by Snips
Hafnium? Did you just make that word up? is it like unobtainium used in that dances with smurf's filck by James Cameron?

http://en.wikipedia.org/wiki/Hafnium
Kúsař 20th January 2011, 15:50 Quote
Quote:
Originally Posted by Bindibadgi
Intel's advantage is that it's costs are lower because it does everything itself, so it can optimise a longer process. However if you're GloFo or TSMC, you have to absorb the cost or your customers product probably becomes less or uncompetitive. It's particularly a problem for AMD, who has to compete with Intel, and usually does so on price.

It might not be such an advantage if you think about it. GloFo is agressively expanding to compete with TSMC as they definitely plan to manufacture more than AMD's CPUs. Once they've got new fabs running their "playground" and cashflow will be definitely bigger than Intel's(speaking about manufacturing:)), unless Intel open it's fabs for others. nVidia, "ATi" or ARM will definitely try to take advantage of multiple manufacturers and this will in turn drive manufacturing/technology processes forward.
Enzo Matrix 20th January 2011, 16:43 Quote
So will AMD's new 32nm products be produced using gate-first or gate-last? This wasn't made clear as the first paragraph indicates they will use the gate-first while the second to last paragraph hints they will use gate-last.
Bindibadgi 20th January 2011, 16:54 Quote
32nm will be Gate First. 22/20 will be Gate Last
Xir 20th January 2011, 17:16 Quote
Quote:
Originally Posted by Kúsař
Once they've got new fabs running their "playground" and cashflow will be definitely bigger than Intel's(speaking about manufacturing
Don't underestimate just how big Intel is...
Before GloFo split off, AMD was about 1/10th of Intel...that's a lot of room to pick up.
Quote:
Intel's advantage is that it's costs are lower because it does everything itself, so it can optimise a longer process
That's the downside of the GloFo Spinoff, AMD used to have this as well (though on a much smaller scale. Dresden beeing effectively it's only CPU-plant.
Suppose it still is as far as high-end devices are concerned. Then again, I don't know how deep the AMD/GloFo split really goes. I guess they still optimise everything in Dresden for AMD's process.
Snips 24th January 2011, 09:16 Quote
Quote:
Originally Posted by jrs77
Quote:
Originally Posted by Snips
Hafnium? Did you just make that word up? is it like unobtainium used in that dances with smurf's filck by James Cameron?

http://en.wikipedia.org/wiki/Hafnium

Thanks mate, I was only having a quick stab at humour.
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