The Extreme Physics Pushing Moore’s Law to the Next Level

We’re suiting up to take you inside a clean
room that’s building an engineering marvel that’ll push the entire electronics industry
to the next frontier. They’re both amazing machines and scary machines. There’s an enormous
amount of complexity with them. There’s an enormous number of things that can potentially
go wrong. It’s something that you don’t necessarily sleep well at night, just having the machine
on your floor. It’s about the size of a school bus, weighing over 180,000 kilograms,
with over 100,000 parts, and 3,000 interlocking cables. Pop the hood and you’ll see lasers
shooting tiny droplets of tin, generating plasma that’ll get collected and reflected
by a series of mirrors, to then etch nanoscale patterns onto chips that’ll eventually go
into your next cell phone. And after 30 years of innovations in physics, chemistry, and
material science, it’s about ready for its debut. An integrated circuit, or chip, is
one of the biggest innovations of the 20th century. It launched a technological revolution,
created Silicon Valley, and everyone’s got one in their pocket. But if you zoomed in
on one of those chips, I mean, really zoomed in, you’d find a highly complex, nanoscale
sized city that’s expertly designed to send information back and forth. Semiconductor
lithography is the ultimate alchemy, turning sand into gold. You start with the silicon
wafer. You add insulators, add something called a gate which you apply a voltage to it, and
it turns on or off the flow of electrons. That’s the little switch that’s sort of does
the zero to one’s that you always hear about You build up a sequence of
layers. The network, the streets and buildings that you need in order to make these transistors
and interconnect those transistors. At the end you can turn that into something that
has substantially more value than a bucket of sand. At big tech conferences, chip manufacturers
will announce they’ve hit impossibly small new milestones, like 22nm then 14nm and 10nm
designs. That means they’ve found a way to shrink the size and increase the number
of features on a chip, which ultimately improves the overall processing power. This is what’s
been driving the semiconductor industry – a drumbeat called Moore’s Law. Moore’s Law
is an expectation. It’s not a natural law. It’s an expectation that we innovate at a pace
of roughly doubling the density every two years. All of those things allow us to offer
better products, allow us to offer cheaper products with the same capability and that
in turn drives the demand for the overall industry. That means that we’ve got to be
able to cram in, more and more functionality per square millimeter on a chip. All the designs and
streets and everything have to be smaller and smaller in dimensions. Moore’s Law has
been predicted to be dying for a long time and yet it never is. Because each generation
of engineers knows it’s their expectation to keep working on it, to keep going at a
certain pace. The core technique at the heart of this expectation is called photolithography. It’s
a chip manufacturing process that’s similar to darkroom photography, but instead of a
negative for a picture, they’re using something called a mask or reticle to expose a geometric print. It’s
basically a projection system where we have a light source, a mask or reticle, which is
the blueprint, then the wafer. And we have to manage the light on the way through to
get a perfect reproduction of that pattern on a silicon wafer. That enables you to build
all of the billions of transistors that you need in order to make a functional chip. The
light sources are lasers, created from a mixture of gases, like carbon dioxide or argon fluoride.
When excited by an electric current, the gas molecules will emit laser radiation that are
then tuned to a specific wavelength that imprints the chip design. There’s a drive to get
the light source to shorter and shorter wavelengths, because the shorter it gets, the more transistors
you can cram onto a chip. In terms of the electromagnetic spectrum, what we can see
visibly is about 400 and 650 nanometers. The chip industry’s gone from 365 nm wavelengths
to 248 nanometers to something called argon fluoride immersion. So argon fluoride refers to a wavelength, 193 nanometers. It is produced using a deep ultraviolet laser light source. The industry
tried to go to 157 nanometer light, and that failed after companies had invested hundreds
of millions of dollars in it. The field then had to invent new technical tricks for the
systems in use today. They actually put water in between the bottom lens element and the
wafer, because the wavelength of light in water is quite a bit shorter. When I first
heard about it, I thought it was just crazy. You’re going to get water all over the stages,
and the electronics inside the tool. There was some very clever engineering that allowed
them to contain that water in a little puddle as the wafer is going back and forth at about 700 millimeters a second. But that turns out to be coming near the end of its ability to produce even finer and finer
features. So to keep Moore’s Law on track without breaking the laws of physics, chip
manufacturers have been racing to bring this technology online: Extreme Ultraviolet
Lithography. It takes the wavelength of light from 193 nanometers down to 13.5. The jump
is much larger than what we would normally do. And that’s partly because it’s more of
a disruptive technology. The first academic work on EUV was done in 1986, when I was still
an undergraduate in college. Through my whole career, we’ve been hearing that EUV was coming.
There was so many fundamental problems with using these soft x-ray wave lengths for a
lithography tool. We’re down to the point where the amount of variation can be measured
in atoms. And so you have to work very hard to have a control of those dimensions. And
that is where ASML comes in. ASML is the most important tech company you’ve never heard
of. We build the big machines that make small chips. EUV was a massive step for us to undertake.
Not only did we need to have an entirely new scanner because we had to work in a vacuum
and at wavelengths where you need to have only reflective optics which required a huge
amount of innovation. But we also needed a new light source as well. In fact, it’s
the first time ever, that we’ve needed to change the light source and huge elements
of the scanner design at the same time. But for this story, we’re just going to focus
on the lasers. Here’s how they work in the machine. The source of the light is a
tiny little droplet of tin. They’re smaller than the diameter of a human hair in which
we fire across the vessel and then we intercept those with a pulsed laser beam of very high
power. And I have to hit it with an accuracy of just a few microns even though it’s traveling
at, let me say at the speed in excess of the speed limit. It forms a plasma that emits EUV light. There’s
a collector mirror that collects that light and sends it into the scanner. Then there
are four mirrors that essentially shape that light into a slit that bounces off the reticle. You
will see a reticle stage doing this, and a wafer stage doing this. And what is happening
is step and scan. Which basically means we continue to reproduce that particular pattern
over and over again. Just to give you a sense of the mechanical complexity even, the wafer
stage itself is something like 200 kilograms in weight and yet it’s able to accelerate
faster than a fighter jet. The thing that probably had people the most skeptical was, getting the power on the source up. When we started out we didn’t generate the power that
we wanted and we struggled at the beginning to understand why. Every year it was slipping
out, and the actual power we were getting was stuck around very low levels, impractical
levels. We continued to dive into looking more fundamentally at the basic plasma physics.
What were we missing? It was around about 2015 where we finally unlocked the secret.
It’s all about exactly controlling how you deliver that energy to the droplet and then
how you would deliver it to the tin afterwards. It becomes very critical in pushing that conversion
efficiency up. You don’t just need to hit the tin droplet with one laser pulse but,
in fact, two. The first of those pulses, shapes the target in a way that enables us to get
this high conversion efficiency and then the second pulse of course, generates that very
hot plasma that we need for generating 13.5 nanometers at high power. Once we crested
that, it became, I wouldn’t say easy, but at least we saw the path and we were able
to make changes to the system and we could see the immediate benefit. We actually still do work looking at how do we continue to push
the power and the features of the light source that will support future scanners. Bunny suits
are required around these precision tools, because the tiniest particle could kill a
wafer pattern. The major
source of particles in a clean room is actually the people. The equipment generally, unless
something is actually scraping, something’s misadjusted, they don’t generate particles.
The bunny suits are to protect the tools, and the wafers from the contamination. Here
we have, largely the manufacturing activities as associated with the droplet generator.
We also have an area we call integration where we look at the entire source and how it performs. When you go in to look at an EUV source, you see a large vessel with lots of interconnection
everything. We have gas, power, water, etc. that’s needs to be delivered. We’ll
see a beam transport system. So where we actually bring the high power laser beam into the vessel.
ASML has been shipping this machine to chip manufacturers and it takes 40 freight containers,
spread over 20 trucks and 3 cargo planes just to ship one of them. This is an army of people
putting things together and pushing the edge of technology to make it work at all. And
then of course having to make it work day in and day out.The EUV scanner is the most
technically advanced tool of any kind, that’s every been made. It’s so far from normal human
experience. I can’t think of anything that has pushed the envelope in so many areas.
There were many knowledgeable people in the field who just said. “You can never
make a practical tool this way.” We’re just starting to enter into high volume manufacturing
with EUV powered scanners and in fact, we’re just starting to see some end products that
are actually coming out that have chips that have been enabled by EUV technology. There’s
an insatiable amount of data, so you can build chips to store data, process data, move data
around. The whole cloud is lots and lots of chips, doing all three of those things. I
was talking with some people that are building the next particle accelerators and they’re
going to generate trillions of events every second. And there’s no way to make sense of
all of that even with this generation of computers. So you’ve got to go build ever
faster computers, larger data storage, just to make sense of the science that’s going
on. Part of predicting the future is around diagnosing trends in technology. If you don’t
know what the future holds, are you afraid of that or are you encouraged by it? And I’m
in the category of being encouraged by it because there’s things to do that you haven’t done
before, things to create that you haven’t created before. And then you may not set out
to change the world, but we changed the world one step at a time.

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