New Math

It was nice when we had round numbers to work with. It was pretty simple to move from 180nm to 120nm and then to 90nm. Then the half nodes started—45/40, 32/28 and 22/20nm.

After 14nm we are poised dangerously over the single-digit process nodes. Intel is working on 10nm, to be followed by 7nm or 5nm. Other companies are looking at 11nm, to be followed by 8nm, 6nm or something even further down the road.

So why so much confusion over which is the real next node? The answer, depending upon who you ask, doesn’t appear to be grounded in anything other than marketing and some rather vague measurements that don’t seem to be the same from one foundry to the next. If you can do 20nm it’s assumed to be better than 22nm, even if in reality you’re only doing 20.5 or 21.5. And if you can offer more instructions per second or more cores its considered better than if you can offer fewer—regardless of whether a particular application can take advantage of either of them.

This is about to hit an entirely new pitch (no pun intended) when we get to stacked die. If you can add a 14nm processor core into a proven stack of analog and memory, replete with finFETs (at least somewhere on the chip or in the package), SOI substrates (also somewhere on the chip) and massive pipes for processing (even if they’re not used) then who’s going to question it. Most of this stuff gets delivered as a black box to chipmakers and integrators, anyway. If it can be marketed more effectively, all the better.

The big fear isn’t that we can’t hit 4nm because it’s technologically impossible. It appears that the roadmap for some chips will extend beyond the nanometer range and well into Angstroms. New atomic structures will replace ones we use today and everyone will scoff at the days when we even considered etching masks with EUV, and designs will be based upon manipulation of subatomic particles that are still in the realm of theoretical physics. At 10nm or so we’ll move into the quantum world, and that will become the future—at least for awhile.

But all of this hedging over exactly what number comes next will become important for a couple reasons. One is that everything inside a chip needs to be measured, and metrology is supposed to be a very exact science. Mathematicians like to brag that their area of expertise is the only exact science. Maybe, but applied math isn’t so exact—particularly in the hands of marketers. And second, these chips need to be designed and verified, and the world of back-end metrology is rapidly moving forward into the design process because of the risk of getting something wrong.

These two worlds need to meet on some very exact numbers that are relatively standard, and they need to integrate with other very exact numbers. Right now it’s hard to build confidence in numbers that seem to change with the wind.