Intel goes heavy metal and turns it up to 11. But it's not the popular choice

12 November 2007

Intel is spending a lot of time telling people, once again, how much of a breakthrough it has made in introducing metal gates - reversing a trend that Intel's founders began back in 1967 when they developed the first silicon-gate process at Fairchild. The Penryn processors are not just 45nm processors, they are "45nm hafnium-based high-k metal gate" chips.

The return to the metal-gate story is because the processors have entered production: reverse-engineering specialist Chipworks is etching away the top of its sample right now to see what lies underneath. So the 45nm generation is underway. And, based on the combination of metal gates and 45nm, Intel looks to be way out in front. But it's not necessarily the case. Foundry TSMC has started running customer wafers through its most advanced fab. We can expect the chips from those wafers to go on sale soon. Matsushita has already got manufacturing runs of its Uniphier chip.

Where Intel does seem to be going it alone is on metal gates. So, it should come as no surprise that the company is focusing attention on that part of the process. However, metal gates are not necessary for making 45nm devices, only those that are likely to burn a lot of power, such as PC processors. For those operating in the low-power segments, the metal gate is something of a luxury. And it's a luxury that a lot chipmakers are avoiding, at least for this generation. Only IBM has said it will use them and it has yet to show off any chips made on a 45nm process.

Although the combination of metal and a dielectric with a higher dielectric constant than silicon dioxide stops current flowing out of the transistor out through the supposedly insulating gate, that form of leakage is only one small part of the overall power loss. In a high-speed chip such as a PC processor, most of the leakage is down to the transistor passing electricity even when it is supposedly turned off. These days, transistors don't so much switch between on and off; they go from on to less-on. As a result, most of the changes needed to deal with leakage have to happen during the design phase. And, those changes cut gate leakage as much as the other, more bothersome form: subthreshold leakage.

So, other chipmakers do not share Intel's enthusiasm for metal gates. They don't want the extra cost of shipping in sophisticated and slow equipment that lovingly deposits the novel high-k dielectric one atomic layer at a time. Even Intel may not choose to use metal gates on the products it plans for the consumer-electronics market.

TSMC last year said it was developing a metal-gate process for 45nm but, as the process got nearer to production, found that a more conventional gate structure was all that it needed. The foundry is looking at the metal gate option seriously for the 32nm process and will, if a customer really wants it, think about putting a metal gate on the existing 45nm process. But they are really going to have to want it.

However, Intel's move won't shove up the cost of making Penryns that much, it seems. In comparison with previous desktop processors, the die is pretty small. The penny you see sitting on a wafer full of Penryns in the publicity shots gives a very good idea of how small the chip is. That means Intel can get a lot more onto a wafer, reducing its overall production cost. This, most likely, more than offsets the increase in cost caused by the use of the more complex metal-gate process. And it gives Intel a potentially strong lead in any price war that it might conduct with AMD to push the advantage it currently holds. There are other companies with 45nm devices, but AMD is not one of them.