[four] things start making a
51% of the time they make the right choice and 49% of the wrong
It's going to be a very inefficient system to do all the error correction to correct for that
And so this is why we often the moore's law the end of its being predicted simply because we are getting down to these
tiny Tiny scales first time I came across
Integrated circuits was when I was lucky enough to be working years ago at [Acorn] at the time at which
Steve furber and Roger Wilson, we're designing the arm processor and at that point
We were all very excited [about] three Micron technology. That was the feature size of the transistors three Microns
Which today is huge and today were doing it you know 28 and 22 nanometers
[modules] interesting we'll be hearing about it for years first coined back in the
70s
By gordon Moore of intel at the time it was an empirical observation. I was an observation of
The number of components that could be built on an integrated circuit
and their cost
It's often simply quoted as you know every generation
We were doubling in complexity, but slightly more nuanced than that we look at
the cost
I'm going to use a log scale here. So we're going to go 110
100
buton
Thousand
to the four and along here
We'll look at number of components
Moore's Observation was over a series of time we started off
The cost was quite high and we could integrate
you know some small number of
Components and as you added more and more components the cost per component went back up
So the point is there was a sweet spot that was. Oh there was a size of
semiconductor of
integrated semiconductor
That was most cost effective. He first time the group. This was 1962 what he observed was [that] at each generation
It was a sweet spot
and that's what's often referred to as moore's [law] is the doubling every generation and the generation is each time we
reduce what we refer to as the feature size of the components reduce the size of the
transistor and the wire and of course if we have the dimension of it then because it's a flat surface we
Quadruple multiply [by] for the number of components we get on the chip first time I came across
Integrated circuits was when I was lucky enough to be working here years ago at Acorn at the time at which
Steve furber Roger Wilson, we're designing the arm processor and at that point. We were all very excited about three Micron technology
That was the feature size of the transistors three Microns which today is huge and today. We're doing it. You know
28 and 22 nanometers are
much smaller feature size, so
What what does [that] actually mean [maybe] which worthwhile thinking about you know how we actually manufacture?
Semiconductors just to get an understanding of and when we're referring to these you know what does this mean and then?
some of the issues that we'll get eventually as we
Shrink these devices small and smaller we'll get to the issues that are causing us
Concerns about Moore's law and the fact that it's you know it's slowing down, [and] it can't continue forever
the original
Transistors were actually made by just lobbing together our various bits of semiconductor material and
In fact as a brilliant picture you'll be able to find the first
Transistor by Shakti when he was at bell labs just showing you how this stuff was glued together, but essentially to build a transistor
we need some semiconductor materials that
That are doped with ions
that give them either a slightly you know and a
lack of electrons in their crystal structure or an excess of electrons
And they're either referred to as p or n materials which refer to as p doping or n doping of the semiconductor material
so when we build silicon chips taking a cross-section of
Some silicon material then we dope an area of it
with what we refer to as this p material and then
maybe another
[area] with these n material in it and as we apply electric charge to this we switch on and off the current
flow through this area of the semiconductor and that gives us the basic switching function
We need and from that we can build up all the more complex logic gates in order [to] build this the way
We do it is very similar to photography a process called lithography
where we start with our semiconductor material and
We put a mask over the top of it then we diffuse in from a gas
Lots of our little molecules here flying around this P-type material it
diffuses into the silicon and that gives us our doped region
And then the next step would be similar thing we start off with our existing region
And then we put on a different resistance layer
And then we do fit with our n-type material and we build up the small zone [obviously] [do] it for less time
So it doesn't go all the way through and this process of laying on resist material and then itching it off the material is
photosensitive, we've put a
Essentially a negative on top of the the chip
show you shiny ultraviolet light through it and
the photoresist reacts under that and then we can etch it away with some chemical leaving some of the resist and then we can
Dope and it's very similar to how we've built printed circuit boards for years. It's just a much smaller scale, so
[as] we want to build smaller and smaller
Transistors, we've had to understand how to build
essentially the Masks
For the chips and these these masks are multiple layers
Including not just the p and the n layers, but [also] metal layers as well for the wiring on the chip
It's each generation is required better understanding more complex
Optical systems and and all sorts of things like that, so that's what we're going on for years
And that's this this same mechanism. These are the basis of all integrated circuits whether they're
processors, whether they're
With their memory devices there are subtle distinctions in the details of the layerings and the type of dopings
We use that make them more efficient for one use or another?
Silicon is not the only material [we] [use] [for] semiconductors for example photonic devices for lasers we often use
Things like gallium Arsenide with which so called three five semiconductors so long
But it's the basis of all our silicon chips and in essence
Know as these feature sizes get smaller and smaller
We start getting to the point where if we look at these areas of the transistor at some point as we shrink this?
The question is how many atoms are there in here or ions of the dopant material?
And as it gets smaller and smaller the [number] gets less and less
And that therein lies one problem, which is as we get to very small numbers of atoms
the behavior we rely on the quantum mechanics behavior of the
Transistor the probability that it switches in the right way starts to start you know the chances that does the right thing start to reduce
Night there's always been a problem with any of these systems
There's usually two places in which it's stable, and you're trying to switch from one place to the other
and
It's just the probability that these will do the wrong thing and as we get down to tiny tiny transistors
There's serious problem that there aren't many
Atoms that are actually at the heart of making that decision, and if they don't all jump decide to jump the same way
Then it may not do what we expect so the prediction of moore's law that [it] will run. I is a statement of the transistors
You know starting to do the unlikely thing too often?
And the point at which you know we've used error correction and other techniques to try to correct the problems that we're getting
you know that will take us so far, but at some point with you know if the things start making a
51 percent of the time they make the right choice and 49 percent of the wrong
It's going to be a very inefficient system to do all the error correction to correct for that
And so this is why we often the moore's law the end of its being predicted simply because we are getting down to these
Tiny tiny scales, there's plenty of other things we still have available to us
I mean many modern [chips] have vast arrays of the chip that are just laid [down] to Memory arrays
And we can ask questions [about] you know are they the best?
Architectures given we have so many billions of transistors are we doing the best thing with them
And then finally something that actually it dates back a long way as well
[I] often find myself going back to what seems like prehistory of computing for many but
Back in the days when I did my phd one of my colleagues did
Work on 3D chip design where we stack up the chips on [top] of each other and hence?
Continue to get you know doublings in Density within a certain area doesn't quite get us the same cost savings
but it does give us [and]
The ability to have very dense computing systems by stacking and we've already seen that a number of commercial products that come available
Things that can affect this radiation there's one public only that will fall [over] like that won't move here. We go ready
The system works [look] at them
And it's for one of those reasons and for example when we build chips to go into satellites or into deep space missions
We take extreme [measures] to protect the material