It seems that the semiconductor industry can’t go a year without someone raising the tired old flag that is the impending doom of Moore’s Law. Nearly every year there’s a group of people out to see it finally meet its end although to what purpose I could not tell you. However as an industry observer will tell you these predictions have, for the past 5 decades, proved to be incorrect as any insurmountable barrier is usually overcome when the requisite billions are thrown at the problem. However we are coming to a point where our reigning champion behind Moore’s Law, namely planar transistors built on silicon, is starting to reach the end of its life and thus we have been searching for its ultimate replacement. Whilst it seems inevitable that a new material will become the basis upon which we build our new computing empire the question of how that material will be shaped is still unanswered, but there are rumblings of what may come.
For the vast majority of computing devices out there the transistors underneath the hood are created in a planar fashion, I.E. they essentially exist in a 2 dimensional space. In terms of manufacturing this has many advantages and the advances we’ve made in planar technology over the years have seen us break through many barriers that threatened to kill Moore’s Law in its tracks. Adding in that additional dimension however is no trivial task and whilst it’s not beyond our capability to do, indeed my computer is powered by a component that makes use of a 3D manufacturing process, but applying it to something as complicated as a CPU requires an incredible amount of effort. However the benefits of doing so are proving to be many and the transistor pictured above, called a Quantum Well Field Effect Transistor (QWFET), could be the ram with which we break through the next barrier to escalating Moore’s Law.
The main driver behind progress in the CPU market comes from making transistors ever-smaller, something which allows us to pack more of them in the same space whilst also giving us benefits like reduced power consumption. However as we get smaller issues that could be ignored, like gate leakage back when we were still at the 45nm stage, start to become fundamental blockers to progress. Right now, as we approach sizes below 10nm, that same problem is starting to rear its head again and we need to look at innovative solutions to tackle it. The QWFET is one such solution as it has the potential to eliminate the leakage problem whilst allowing us to continue our die shrinking ways.
QWFETs are essentially an extension of Intel’s current FinFET technology. In the current FinFETs electrons are bounded on 3 sides which is what helped Intel make their current die shrink workable (although it has taken them much longer than expected to get the yeilds right). In QWFETs the electrons are bounded on an additional side which forms a quantum well inside the transistor. This drastically reduces the leakage which would otherwise plague a transistor of a sub-10nm size and, as a benefit, significantly reduces power draw as the static power usage drops considerably.
This does sound good in principle and would be easy to write off as hot air had Intel not been working on it since at least 2010. Some of their latest research points to these kinds of transistors being the way forward all the way down to 5nm which would keep Moore’s Law trucking along for quite some time considering we’re just on the cusp of 14nm products hitting our shelves. Of course this is all speculative at this time however there’s a lot of writing on the wall that’s pointing to this as being the way forward. If this turns out to not be the case then I’d be very interested to see what Intel had up their sleeves as it’d have to be something even more revolutionary than this.
Either way it’l be great for us supporters of Moore’s Law and, of course, users of computers in general.
Anyone who’s had a passing interest in computers has likely run up against the notion of Moore’s Law, even if they don’t know the exact name for it. Moore’s Law is a simple idea, approximately every 2 years the amount of computing power than can be bought cheaply doubles. This often takes the more common forms of “computer power doubles every 18 months” (thanks to Intel executive David House) or, for those uninitiated with the law, computers get obsoleted faster than any other product in the world. Since Gordon E. Moore first stated the idea back in 1970 it’s held on extremely well and for the most part we’ve beaten the predictions pretty handily.
Of course there’s been a lot of research into the upper limits of Moore’s Law as with anything exponential it seems impossible for it to continue on for an extended period of time. Indeed current generation processors built on the standard 22nm lithography process were originally thought to be one such barrier, because the gate leakage at that point was going to be unable to be overcome. Of course new technologies enabled this process to be used and indeed we’ve still got another 2 generations of lithography processes ahead of us before current technology suggests another barrier.
More recently however researches believe they’ve found the real upper limit after creating a transistor that consists only of a single atom:
Transistors — the basic building block of the complex electronic devices around you. Literally billions of them make up that Core i7 in your gaming rig and Moore’s law says that number will double every 18 months as they get smaller and smaller. Researchers at the University of New South Wales may have found the limit of this basic computational rule however, by creating the world’s first single atom transistor. A single phosphorus atom was placed into a silicon lattice and read with a pair of extremely tiny silicon leads that allowed them to observe both its transistor behavior and its quantum state. Presumably this spells the end of the road for Moore’s Law, as it would seem all but impossible to shrink transistors any farther. But, it could also points to a future featuring miniaturized solid-state quantum computers.
It’s true that this seems to suggest an upper limit to Moore’s Law, I mean if the transistors can’t get any smaller than how can the law be upheld? The answer is simple, the size of transistors isn’t actually a limitation of Moore’s Law, the cost of their production is.
You see most people are only familiar with the basic “computing power doubles every 18 months” version of Moore’s Law and many draw a link between that idea and the size of transistors. Indeed the size is definitely a factor as that means we can squeeze more transistors into the same space, but what this negates is the fact that modern CPU dies haven’t really increased in size at all in the past decade. Additionally new techniques like 3D CPUs (currently all the transistors on a CPU are in a single plane) have the potential to exponentially grow the number of transistors without needing the die shrinks that we currently rely on.
So whilst the fundamental limit of how small a transistor is might be a factor that affects Moore’s Law it by no means determines the upper limit; the cost of adding in those extra transistors does. Indeed every time we believe we’ve discovered yet another limit another technology gets developed or improved to the point where Moore’s Law becomes applicable again. This doesn’t negate work like that in the linked article above as discovering potential limitations like that better equips us for dealing with them. For the next decade or so though I’m very confident that Moore’s Law will hold up, and I see no reason why it won’t continue on for decades afterward.