July 21, 2025 • 21 mins
The fourth state of matter, plasma, is involved in several aspects of how modern microelectronic components are manufactured. Jeremiah Williams, a professor at Wittenberg University and a program director at the U.S. National Science Foundation, discusses how plasmas are used in semiconductor manufacturing and how understanding plasma physics spurs industrial innovation.
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(00:03):
This is the Discovery Files podcastfrom the U.S.
National Science Foundation.
In a computerized world,
microchips in semiconductorsare vitally important to how things
all around you work, from phonesand televisions to cars and streetlights.
The fourth state of matterplasmas are involved in several aspects
of how modern microelectronic componentsare manufactured, and understanding
(00:25):
the physics of how plasmas workand how they can be precisely controlled
becomes more important as devicesand their parts get smaller.
We're joined by Jeremiah Williams,a professor of physics at Wittenberg
University, where his group focuseson basic research in experimental plasma
physics with applications to spaceenvironments and industrial plasmas.
Doctor Williams is also programdirector here at the U.S.
(00:46):
National Science Foundation.
Doctor Williams,thank you so much for joining me today.
Thank you for having me.
So I want to start with the big question.
What is a plasma?
Plasmas are one of the four naturallyoccurring states of matter.
And I like to think of it
in terms of the other states of matterand how you can distinguish between them.
And it really has to do withhow things behave at the atomic level,
at the level of the atoms in the moleculesthat make up the material.
(01:07):
So if you think about a solid likethis table here, what makes a solid unique
is that the atoms and molecules interactvery strongly with each other,
and as a result, they're locked in placeand they can't really move.
Right.
That'swhat makes them rigid and a solid solid.
Now, if you were to add energy to that,say, take an ice cube,
put it in the stove, turn the heat on thatenergy is being transferred in, and it's
(01:30):
being added to the atoms and molecules,and it's causing these start jiggle some.
And as they jiggle more,which we quantify by the temperature,
that interaction
that's holding them together just becauseof how they interact with each other,
that is not enough to keep them fixedrigidly in place
and as a result, experiencewhat's called a phase transition.
And the ice melts and turns into a water.
(01:52):
So now the atoms and moleculesstill interact strongly, but not so much
that they're fixed in placeand they can move around some.
You add even more energy.
What happensis that thermal energy, the jiggling,
they cause the moleculesto basically spread out and undergo
another phase transitionand turn into a gas. Right.
And now at this point,the only time these atoms and molecules
(02:13):
interact with each otheris when they bump into each other.
You know, if you want to understandwhat's happening with the gas
right here, air molecules,you really have to think about
what's happening when they collidewith each other at that location.
So these collisions determine everything.
Now if you add even more energy, atomsare made up of smaller things, right?
You've got protons and neutrons insidethe nucleus, and you have electrons also.
(02:36):
And these electrons interact withthe nucleus and are sort of bound to that.
But if you had enough energy,you can pull off the electrons.
And now you end up with this mixtureof positively charged ions.
These are the atoms that have had
an electron pulled off the electrons,which are negatively charged,
and then some neutral particles,depending on the kind of plasma you have.
Now, because you've got thismixture of charged particles,
(03:00):
they interact through collisions,
but they also interact through long range,what we call electromagnetic forces.
Right.
So if you have like a magnet on yourfridge, magnets interact at a distance.
It's what we call a long range force.
And so the behavior locally is determinednot just by what's happening locally
but through these long rangeforces as well.
And that's what a plasma is.
So it's essentially an ionized gas.
(03:21):
Where do plasmas come from?
It depends on sort of the settingyou're looking at.
In terms of sortof where plasmas initially came from.
Big bang happened 13.8 billion years ago.
And at that point everything was in aplasma state because there so much energy.
And it literally took hundredsof thousands of years for that plasma
(03:42):
to cool downand return to a gaseous state.
Right.
So plasmas in some senseare the first of the four naturally
occurring states of matter.
Now, as things have cooled, everything'sno longer in the plasma state.
And if we look insort of the visible universe, we can see
plasmas account for about 99%of what we see in the universe, in space.
(04:03):
Stars are basically plasmas.
You can think of them as basically plasmagenerators.
They spit plasma out into space.
That's the solar wind, right?
Which comes and hits the Earth, createsbeautiful aurora that we sometimes see.
On Earth,
we happen to be in an environment whereplasmas just aren't naturally existing,
which is good because it's not necessarilya hospitable place.
We would not dowell if we were in that environment.
(04:25):
But you can make plasmas.
And so, you know,depending on what you want to do with it,
you have different waysof doing it. Right.
So if you want to make semiconductors,you use power supplies to do that.
You know,
there's other applicationslike plasma welding where you use a plasma
to connect material, or plasma cutterswhere you use the plasma to cut.
(04:46):
There's also applications in medicinewhere you can use plasma
to treat wounds, agriculturewhere you can increase crop yields.
So there's lots of practical applicationsthat are created by basically
putting energy into the systemto ionize the gas.
How do they use plasmas in industry?
Plasmas have lots of applicationsacross industry.
(05:08):
So if you think about medicine, plasmasare used in medicine for sterilization.
So you can use it to cleanthe surgical tools before you use them.
You can use it for wound treatment
where the plasmas create these radicalswhen you ionize the gas
and they basically interact with the woundand can speed up the healing process.
(05:30):
You can see it in agriculture
where you would treat seeds or plantsdirectly with the plasma.
And it's been shownthat you can increase the crop yield.
It's used in water purification.
Plasma basically treats the waterto make it safe to drink.
That's one sort of avenue
you can expose materials to plasmato make it hydrophobic.
(05:50):
So if you want your jeans to repel water,you can treat your jeans with plasma.
To do that.
In semiconductors, overhalf the steps where chips are being
made, plasmas are usedsort of throughout the whole process.
Right.
So when you want to make a semiconductor,any type of electronic device
that you might make,you would start off with a silicon wafer.
(06:14):
And the first thing you do is you treatthat with a plasma to clean it.
And then what you would do isyou would create a mask,
which is basically sort of the shapeof the circuit that you want to make.
And those are typically made by takinga laser, hitting a tin to create plasma.
So like a little molten drop of tinthat creates light,
which will then basically createthe pattern on the material.
(06:38):
You can then use the
plasma to basically etch awaythe material,
or to add layers of materialor implant things
so that you make it behave in the waythat you want your chip to behave,
and then you end upwith your microchip at the end.
So there's lots of practical applicationsand how they get used in industry.
(06:58):
How might you control a plasmain this case?
So like if we're thinking aboutplasma etching how are they able to do it?
It's a complicated process.
The nice thing about plasmas is thatbecause they're made up of these charged
particles, you can use what we knowfrom sort of basic physics
and how charged particles behavein different types of fields, right?
(07:22):
So if you think about us on Earth,if I were to drop, you know,
let go of something,we all know that it's going to fall.
And the reason that it falls is gravity.
We can model that as a field.
And basically the object wants to be,go from here to here.
And gravity is what's pulling it down.
Same thing sort of happens
when we're dealing with ions and electronsthat show up in a plasma.
(07:42):
But in this case they're charged.
So we use electric and magnetic forcesto control how they move.
Just like we would use gravity controlhow something moves as it's falling.
So you can create the plasma.
And then you can basically tunethe plasma,
change the parameters of the plasma.
So you get it sort of just right.
And then you can apply these fieldsto control how they move.
(08:04):
But it's a complicated process,particularly as things get faster.
Things it fasterbecause things get smaller.
The features that we are dealing withwhen we're making
these semiconductors,we're on the nanometer scale.
Now, of course, that probably doesn'tmean a whole lot because I don't
you know, most peopledon't think about nanometers, right.
But a couple of ways to think about that.
(08:26):
If you were to pull out
one of your hairs,you'd say that that's 100 microns roughly.
It's about 100,000 timesbigger than a nanometer.
Another way that I like to think about itis if you were to take one of those
silicon wafersthat they used right about an inch across,
and you were to blow that upto the size of the Earth.
The size feature that we're dealing within current generation
(08:48):
semiconductorswould be about five centimeters.
So just around two inches.
So we're dealing with really finesmall structures,
which means that you have to havereally fine control and that
can you control plasmas? Yes.
In principleit's a relatively straightforward process,
but the level of controlthat you have to have
(09:09):
with these highly energetic particlesso that they do damage
in the way that you want right?
To remove the materialor to add material on.
It's very complicated.
What are some of the challengesat that scale?
One case, if we think about memorythat shows up in your phones
and your computers, these are threedimensional structures, right?
(09:32):
So we've gone from whereeverything's two dimensional to now.
They're two dimensional
and really small and really smalland becoming three dimensional.
You can sort of think of itas when you're making one of these memory
chips,you're basically stacking layers up.
You're building your skyscraper,and then you form these holes.
And the way that you do
that is you basically acceleratethe ions that are in the plasma
(09:56):
so that they hit the materialand etch it away.
When they come in, they're coming inat 300 ish times the speed of sound.
So very, very fast.
And you basically use that tothen bore these holes.
Right now, the holesthat they're pouring out are much taller
than they are wide, you know,a hundred times deeper than they are wide.
(10:17):
And so that would be like,you know, you built your skyscraper,
now you're going to put in the elevatorshafts.
You need to have these ionsthat come straight down and sort of bore
your hole out.
And if you're off by just a little bit,right, like, say a 10th of a degree,
your elevator shaft’s 20%wider at the base than it was at the top,
and your elevator is not going to work.
You have to control the directionthat these particles are moving
(10:40):
very, very carefully.
And at the energies that they're moving
so that they can remove materialin the controlled way that you want to.
How are NSF and industrial partnersimpacting this process?
There are a couple of waysthat that happen.
At the NSF,when it was created by Congress
75 years ago, it was with the purposeof advancing science.
(11:01):
Right.
And so what I really like about the NSFis that we fund
what I'd like to think of as curiositydriven research,
research that we don't know whereit's going to end up, but we're doing
because it's an interesting scienceproblem that the community has identified.
And with that,
you neverknow sort of where it's going to end up.
But you often end upwith sort of new understandings,
(11:24):
which then be turned into somethingthat industry might be interested in.
One really nice example,there was a story on the NSF web page,
within the last couple of months,we had, P.I.
at UCLA.
Walter Gekelman and Patrick Pribyl,they worked with Lam Research,
and Lam Research is I thinkit's like an $18 billion a year company.
(11:49):
They make the components that they sellthe semiconductor
manufacturers to make the chips.
And, you know, this process started backand the years are
probably getting them wrong.
But around 2005 ish,
when Patrick had this ideaof how to better control
the direction of the ions,which would be very beneficial
(12:09):
because you want to really control
how the ions are moving to to edge outand remove the material.
And so he built something in his kitchen,which is great.
Is this a laser?
It was a plasma. It was a plasma device.It was a device to make a plasma.
And he had this idea that if you couldcontrol how you were making the plasma.
So basically you sort ofturn it on and off very quickly.
And if you did it in just the right way,you could really sort of shape
(12:34):
how the ions were moving in a waythat would allow you to
then do what they might want to doin making a semiconductor.
And so they worked on it for a bit.
They brought it to industry.
The industry was hesitantbecause it wasn't fully developed.
And so they came to the National ScienceFoundation with a proposal,
and it went through the peerreview process
(12:56):
that we do with all proposals,and it was able to be funded,
and it was funded throughwhat's called the GOALI program,
where basically it's being fundedby core programs to do basic science,
but with an industrial partner,in this case, Lam research.
And they went through
a couple of cycles of thatand after about ten years of funding,
they had really
(13:17):
lots of careful experimentation,figured out how to control the ions.
And it was just released as a product.
It's marketedas their Direct Drive technology,
and it's now a product that you can goand buy.
And it's sitting on floors
in semiconductor manufacturing companiesmaking electronics.
So that's a great example of comingfrom the fundamental research idea.
(13:38):
That.
I'm there, and I made this thingin my kitchen that could.
control this and.
Now it's being used in your. Devices.
I've got this neat idea.
There's a lot of complicated physics,a lot of careful work,
understanding how it worksand then working with the companies
to translate that basic researchinto a commercial product.
(13:59):
I also want to spend some timetalking about some of your background
research stuff,and I want to ask you about Dusty Plasma.
Yes.
Is this the kind of dust we see around us?
Is it like skin? What?What are we talking about?
So the subfield of physicsthat I work in is,
as you said, dusty plasmas and basically
the definition of a plasma that I gave youearlier is a little bit misleading.
That's sort of like the pure plasmathat really doesn't exist in real life.
(14:22):
Most plasmas have particulate matterin it.
Right?
So if you think about space,it's filled with plasma
and there's lots of stuff in space.
Right.
Asteroids, meteors, comets, right?
The comet goes by the sun.You see the beautiful comet trail.
What's happening isthe ice is being blasted off the comet.
So you're getting little ice chunks.
So there's lots of particles.
(14:44):
Now, if these particles are sittingin a plasma,
they're going to collect chargesand become charged too, right.
Because they're
sitting in a plasma environment,which is a bunch of charged particles.
But once they become chargedto become part of the plasma system
and to really understand
everything that's going on, you need totreat the dust as a part of the plasma.
So your dusty plasma is a plasmathat has three charge species.
(15:07):
You have the positive
ions, the negatively charged electrons,and then the dust particles.
And when we talk about dust,dust is really any particulate matter.
All right.
So there have been dusty plasmaexperiments where they have used pollen.
If you think about,
the ionosphere,for people who do ham radio,
(15:29):
in the summer, you can oftencommunicate greater distances away.
Well the reason why is in the summer,the ionosphere is colder
because of how the planet is orientedrelative to the sun.
And that leads to the formation of icecrystals.
Well, the ice is particulate matter
sitting in the ionosphere,which is a plasma, it becomes charged.
And that changeshow radio waves can travel,
(15:52):
so they aren't able to travelin the same way.
And they reflect off and you're able to,you know, communicate further away,
right.
So it can be ice.
It can be any matter. It could be skin.
I wouldn't
want to put skin in one of my devices,but we typically use are small particles,
that are grown in the laboratoryso we can have a sense of what they are.
(16:12):
So they're typically some sort of plasticor silica or glass.
We tend to use dustthat is much more precisely manufactured.
So we know exactly what it is that allowsus to better understand what's going on.
So for my last question,I want to ask about the future
and emerging technologies.
Where would you like to see the field goor where do you think it will go?
(16:33):
Well,if we're talking about plasma physics
generally, that's a complicated questionbecause plasmas are very broad.
So if we think about the plasma physicsportfolio that we have here at the NSF,
we support low temperature plasmas,the types of things that I do.
And on that sidethere's lots of open questions.
What is the charge on the dust
(16:54):
that's not fully understood,but it's an important quantity.
We now have the abilityto make very large magnetic fields.
And that's a new knob that we can useto look at the additional behavior.
There's a project at Auburn University,the Magnetized Dusty Plasma Experiment,
built with an MRI award
from the National Science Foundationjust over ten years ago.
(17:15):
That's a new knobthat allows us to look at things
as we think about going to the moonand Mars.
Well, dust contamination is a real issue.
So being able to controlthe dust is important.
I think there are lots of sortof interesting questions there,
but that's just a small piece.
You have high intensity laserswhere you use lasers
to dolots of really interesting plasma physics.
(17:38):
There's the Zeus facility at Universityof Michigan that is now operational.
They just it 2 petawatt,so the highest power laser in the US,
you can use that to accelerate particles.
So that would enable the next generationof particle physics experiments.
But there's a lot of medical applicationsfor that as well.
(17:58):
You can createextreme environments relevant
to what's happening inside of starsand inside of planets.
Huge parameter space to look at there.
There's currently a design projectto try and push the frontiers further.
That's the NSF OPAL project,which is at the University of Rochester.
That's a three year award that at the end,
they'll have basically a planto build the next generation.
(18:20):
If that were to be funded,
instead of having,Zeus will be three petawatts fairly soon.
This would be a two 25 petawatt beams.
And that would allow us to do thingslike boil the vacuum to create particles
out of nothing, which is just.
Cool stuff Starts to get to whereit's like, what is that?
So if you think about fusion,that's another example of plasmas.
(18:41):
And, you know,there's a lot of questions there.
How does the plasmainteract with the wall?
Is NSF going to fund a.
We're going to build a fusion reactor, no, but are we going to address questions
that are relevant to fusion? Absolutely,right?
Might do the science.That gets us there. Exactly.
But plasma physics isn'tjust in the division of physics,
which is where I sit,you've got GEO space, right?
(19:04):
And in there they look at,you know, the sun and earth
and that connection, as wellas what happens inside the atmosphere.
A lot of plasma physics there.
Space weather. Right?
We've got lots of satellites being ableto understand that and predict that.
That's a big area where I think there'slots of opportunity in engineering.
There's a lot of plasma physicsthat's supported there, in manufacturing
(19:28):
and just trying to understandthe engineering processes.
So there's additional plasma physicsthere.
You know, if you think about semiconductormanufacturing, I think that there's
a lot of exciting possibilities,you know, that's going to be driven by
market needs and then regulationand those, those are hard to predict.
But I think the one thingthat is safe to say is that we are going
(19:49):
to want things that are fasterand more energy efficient,
and there's a lot of questionsthat come in there, right?
I could see lots of interesting examplesof artificial intelligence, right?
When a lot of thesesemiconductors are made,
they come up with whatyou might call recipes, right?
I want this power at this frequency
for this longwith these different conditions, because
(20:11):
that's going to get the plasma closeto sort of making what you want.
The reality is, when you're doing that,there are lots of knobs
that you have to turn,and those knobs have lots of settings
which make it impossibleto find the optimal one.
But you can run several case scenarios,and then maybe you could use machine
learning to say, here's
our input set, here's what the outputis, here's what we really want.
(20:35):
What's the optimal setting.
So you can really sort of fine tune that.
You can do these digital twinswhere you make
a digital replicaof the semiconductor device.
And we've just awarded something wherethey're helping to develop these models
that will allow sort of full scalemodeling of the system
to really understand what's happening,to sort of help drive that process of fine
(20:56):
tuning things, to really
get the right type of environment,to make the kinds of things that you want.
So I think there's lots of excitingopportunities just depends on
sort of what you mean by plasmas,because plasmas really are broad.
Special thanks to Jeremiah Williams.
For The DiscoveryFiles, I'm Nate Pottker. Watch video
versions of these conversations on our@NSFscience YouTube channel.
Please subscribe wherever you get podcastsand if you like our program,
(21:17):
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Discover how the U.S.
National Science Foundationis advancing research at nsf.gov.
This is the Discovery Files podcastfrom the U.S.
National Science Foundation.
In a computerized world,
microchips in semiconductorsare vitally important to how things
all around you work, from phonesand televisions to cars and streetlights.
The fourth state of matterplasmas are involved in several aspects
of how modern microelectronic componentsare manufactured, and understanding
(00:25):
the physics of how plasmas workand how they can be precisely controlled
becomes more important as devicesand their parts get smaller.
We're joined by Jeremiah Williams,a professor of physics at Wittenberg
University, where his group focuseson basic research in experimental plasma
physics with applications to spaceenvironments and industrial plasmas.
Doctor Williams is also programdirector here at the U.S.
(00:46):
National Science Foundation.
Doctor Williams,thank you so much for joining me today.
Thank you for having me.
So I want to start with the big question.
What is a plasma?
Plasmas are one of the four naturallyoccurring states of matter.
And I like to think of it
in terms of the other states of matterand how you can distinguish between them.
And it really has to do withhow things behave at the atomic level,
at the level of the atoms in the moleculesthat make up the material.
(01:07):
So if you think about a solid likethis table here, what makes a solid unique
is that the atoms and molecules interactvery strongly with each other,
and as a result, they're locked in placeand they can't really move.
Right.
That'swhat makes them rigid and a solid solid.
Now, if you were to add energy to that,say, take an ice cube,
put it in the stove, turn the heat on thatenergy is being transferred in, and it's
(01:30):
being added to the atoms and molecules,and it's causing these start jiggle some.
And as they jiggle more,which we quantify by the temperature,
that interaction
that's holding them together just becauseof how they interact with each other,
that is not enough to keep them fixedrigidly in place
and as a result, experiencewhat's called a phase transition.
And the ice melts and turns into a water.
(01:52):
So now the atoms and moleculesstill interact strongly, but not so much
that they're fixed in placeand they can move around some.
You add even more energy.
What happensis that thermal energy, the jiggling,
they cause the moleculesto basically spread out and undergo
another phase transitionand turn into a gas. Right.
And now at this point,the only time these atoms and molecules
(02:13):
interact with each otheris when they bump into each other.
You know, if you want to understandwhat's happening with the gas
right here, air molecules,you really have to think about
what's happening when they collidewith each other at that location.
So these collisions determine everything.
Now if you add even more energy, atomsare made up of smaller things, right?
You've got protons and neutrons insidethe nucleus, and you have electrons also.
(02:36):
And these electrons interact withthe nucleus and are sort of bound to that.
But if you had enough energy,you can pull off the electrons.
And now you end up with this mixtureof positively charged ions.
These are the atoms that have had
an electron pulled off the electrons,which are negatively charged,
and then some neutral particles,depending on the kind of plasma you have.
Now, because you've got thismixture of charged particles,
(03:00):
they interact through collisions,
but they also interact through long range,what we call electromagnetic forces.
Right.
So if you have like a magnet on yourfridge, magnets interact at a distance.
It's what we call a long range force.
And so the behavior locally is determinednot just by what's happening locally
but through these long rangeforces as well.
And that's what a plasma is.
So it's essentially an ionized gas.
(03:21):
Where do plasmas come from?
It depends on sort of the settingyou're looking at.
In terms of sortof where plasmas initially came from.
Big bang happened 13.8 billion years ago.
And at that point everything was in aplasma state because there so much energy.
And it literally took hundredsof thousands of years for that plasma
(03:42):
to cool downand return to a gaseous state.
Right.
So plasmas in some senseare the first of the four naturally
occurring states of matter.
Now, as things have cooled, everything'sno longer in the plasma state.
And if we look insort of the visible universe, we can see
plasmas account for about 99%of what we see in the universe, in space.
(04:03):
Stars are basically plasmas.
You can think of them as basically plasmagenerators.
They spit plasma out into space.
That's the solar wind, right?
Which comes and hits the Earth, createsbeautiful aurora that we sometimes see.
On Earth,
we happen to be in an environment whereplasmas just aren't naturally existing,
which is good because it's not necessarilya hospitable place.
We would not dowell if we were in that environment.
(04:25):
But you can make plasmas.
And so, you know,depending on what you want to do with it,
you have different waysof doing it. Right.
So if you want to make semiconductors,you use power supplies to do that.
You know,
there's other applicationslike plasma welding where you use a plasma
to connect material, or plasma cutterswhere you use the plasma to cut.
(04:46):
There's also applications in medicinewhere you can use plasma
to treat wounds, agriculturewhere you can increase crop yields.
So there's lots of practical applicationsthat are created by basically
putting energy into the systemto ionize the gas.
How do they use plasmas in industry?
Plasmas have lots of applicationsacross industry.
(05:08):
So if you think about medicine, plasmasare used in medicine for sterilization.
So you can use it to cleanthe surgical tools before you use them.
You can use it for wound treatment
where the plasmas create these radicalswhen you ionize the gas
and they basically interact with the woundand can speed up the healing process.
(05:30):
You can see it in agriculture
where you would treat seeds or plantsdirectly with the plasma.
And it's been shownthat you can increase the crop yield.
It's used in water purification.
Plasma basically treats the waterto make it safe to drink.
That's one sort of avenue
you can expose materials to plasmato make it hydrophobic.
(05:50):
So if you want your jeans to repel water,you can treat your jeans with plasma.
To do that.
In semiconductors, overhalf the steps where chips are being
made, plasmas are usedsort of throughout the whole process.
Right.
So when you want to make a semiconductor,any type of electronic device
that you might make,you would start off with a silicon wafer.
(06:14):
And the first thing you do is you treatthat with a plasma to clean it.
And then what you would do isyou would create a mask,
which is basically sort of the shapeof the circuit that you want to make.
And those are typically made by takinga laser, hitting a tin to create plasma.
So like a little molten drop of tinthat creates light,
which will then basically createthe pattern on the material.
(06:38):
You can then use the
plasma to basically etch awaythe material,
or to add layers of materialor implant things
so that you make it behave in the waythat you want your chip to behave,
and then you end upwith your microchip at the end.
So there's lots of practical applicationsand how they get used in industry.
(06:58):
How might you control a plasmain this case?
So like if we're thinking aboutplasma etching how are they able to do it?
It's a complicated process.
The nice thing about plasmas is thatbecause they're made up of these charged
particles, you can use what we knowfrom sort of basic physics
and how charged particles behavein different types of fields, right?
(07:22):
So if you think about us on Earth,if I were to drop, you know,
let go of something,we all know that it's going to fall.
And the reason that it falls is gravity.
We can model that as a field.
And basically the object wants to be,go from here to here.
And gravity is what's pulling it down.
Same thing sort of happens
when we're dealing with ions and electronsthat show up in a plasma.
(07:42):
But in this case they're charged.
So we use electric and magnetic forcesto control how they move.
Just like we would use gravity controlhow something moves as it's falling.
So you can create the plasma.
And then you can basically tunethe plasma,
change the parameters of the plasma.
So you get it sort of just right.
And then you can apply these fieldsto control how they move.
(08:04):
But it's a complicated process,particularly as things get faster.
Things it fasterbecause things get smaller.
The features that we are dealing withwhen we're making
these semiconductors,we're on the nanometer scale.
Now, of course, that probably doesn'tmean a whole lot because I don't
you know, most peopledon't think about nanometers, right.
But a couple of ways to think about that.
(08:26):
If you were to pull out
one of your hairs,you'd say that that's 100 microns roughly.
It's about 100,000 timesbigger than a nanometer.
Another way that I like to think about itis if you were to take one of those
silicon wafersthat they used right about an inch across,
and you were to blow that upto the size of the Earth.
The size feature that we're dealing within current generation
(08:48):
semiconductorswould be about five centimeters.
So just around two inches.
So we're dealing with really finesmall structures,
which means that you have to havereally fine control and that
can you control plasmas? Yes.
In principleit's a relatively straightforward process,
but the level of controlthat you have to have
(09:09):
with these highly energetic particlesso that they do damage
in the way that you want right?
To remove the materialor to add material on.
It's very complicated.
What are some of the challengesat that scale?
One case, if we think about memorythat shows up in your phones
and your computers, these are threedimensional structures, right?
(09:32):
So we've gone from whereeverything's two dimensional to now.
They're two dimensional
and really small and really smalland becoming three dimensional.
You can sort of think of itas when you're making one of these memory
chips,you're basically stacking layers up.
You're building your skyscraper,and then you form these holes.
And the way that you do
that is you basically acceleratethe ions that are in the plasma
(09:56):
so that they hit the materialand etch it away.
When they come in, they're coming inat 300 ish times the speed of sound.
So very, very fast.
And you basically use that tothen bore these holes.
Right now, the holesthat they're pouring out are much taller
than they are wide, you know,a hundred times deeper than they are wide.
(10:17):
And so that would be like,you know, you built your skyscraper,
now you're going to put in the elevatorshafts.
You need to have these ionsthat come straight down and sort of bore
your hole out.
And if you're off by just a little bit,right, like, say a 10th of a degree,
your elevator shaft’s 20%wider at the base than it was at the top,
and your elevator is not going to work.
You have to control the directionthat these particles are moving
(10:40):
very, very carefully.
And at the energies that they're moving
so that they can remove materialin the controlled way that you want to.
How are NSF and industrial partnersimpacting this process?
There are a couple of waysthat that happen.
At the NSF,when it was created by Congress
75 years ago, it was with the purposeof advancing science.
(11:01):
Right.
And so what I really like about the NSFis that we fund
what I'd like to think of as curiositydriven research,
research that we don't know whereit's going to end up, but we're doing
because it's an interesting scienceproblem that the community has identified.
And with that,
you neverknow sort of where it's going to end up.
But you often end upwith sort of new understandings,
(11:24):
which then be turned into somethingthat industry might be interested in.
One really nice example,there was a story on the NSF web page,
within the last couple of months,we had, P.I.
at UCLA.
Walter Gekelman and Patrick Pribyl,they worked with Lam Research,
and Lam Research is I thinkit's like an $18 billion a year company.
(11:49):
They make the components that they sellthe semiconductor
manufacturers to make the chips.
And, you know, this process started backand the years are
probably getting them wrong.
But around 2005 ish,
when Patrick had this ideaof how to better control
the direction of the ions,which would be very beneficial
(12:09):
because you want to really control
how the ions are moving to to edge outand remove the material.
And so he built something in his kitchen,which is great.
Is this a laser?
It was a plasma. It was a plasma device.It was a device to make a plasma.
And he had this idea that if you couldcontrol how you were making the plasma.
So basically you sort ofturn it on and off very quickly.
And if you did it in just the right way,you could really sort of shape
(12:34):
how the ions were moving in a waythat would allow you to
then do what they might want to doin making a semiconductor.
And so they worked on it for a bit.
They brought it to industry.
The industry was hesitantbecause it wasn't fully developed.
And so they came to the National ScienceFoundation with a proposal,
and it went through the peerreview process
(12:56):
that we do with all proposals,and it was able to be funded,
and it was funded throughwhat's called the GOALI program,
where basically it's being fundedby core programs to do basic science,
but with an industrial partner,in this case, Lam research.
And they went through
a couple of cycles of thatand after about ten years of funding,
they had really
(13:17):
lots of careful experimentation,figured out how to control the ions.
And it was just released as a product.
It's marketedas their Direct Drive technology,
and it's now a product that you can goand buy.
And it's sitting on floors
in semiconductor manufacturing companiesmaking electronics.
So that's a great example of comingfrom the fundamental research idea.
(13:38):
That.
I'm there, and I made this thingin my kitchen that could.
control this and.
Now it's being used in your. Devices.
I've got this neat idea.
There's a lot of complicated physics,a lot of careful work,
understanding how it worksand then working with the companies
to translate that basic researchinto a commercial product.
(13:59):
I also want to spend some timetalking about some of your background
research stuff,and I want to ask you about Dusty Plasma.
Yes.
Is this the kind of dust we see around us?
Is it like skin? What?What are we talking about?
So the subfield of physicsthat I work in is,
as you said, dusty plasmas and basically
the definition of a plasma that I gave youearlier is a little bit misleading.
That's sort of like the pure plasmathat really doesn't exist in real life.
(14:22):
Most plasmas have particulate matterin it.
Right?
So if you think about space,it's filled with plasma
and there's lots of stuff in space.
Right.
Asteroids, meteors, comets, right?
The comet goes by the sun.You see the beautiful comet trail.
What's happening isthe ice is being blasted off the comet.
So you're getting little ice chunks.
So there's lots of particles.
(14:44):
Now, if these particles are sittingin a plasma,
they're going to collect chargesand become charged too, right.
Because they're
sitting in a plasma environment,which is a bunch of charged particles.
But once they become chargedto become part of the plasma system
and to really understand
everything that's going on, you need totreat the dust as a part of the plasma.
So your dusty plasma is a plasmathat has three charge species.
(15:07):
You have the positive
ions, the negatively charged electrons,and then the dust particles.
And when we talk about dust,dust is really any particulate matter.
All right.
So there have been dusty plasmaexperiments where they have used pollen.
If you think about,
the ionosphere,for people who do ham radio,
(15:29):
in the summer, you can oftencommunicate greater distances away.
Well the reason why is in the summer,the ionosphere is colder
because of how the planet is orientedrelative to the sun.
And that leads to the formation of icecrystals.
Well, the ice is particulate matter
sitting in the ionosphere,which is a plasma, it becomes charged.
And that changeshow radio waves can travel,
(15:52):
so they aren't able to travelin the same way.
And they reflect off and you're able to,you know, communicate further away,
right.
So it can be ice.
It can be any matter. It could be skin.
I wouldn't
want to put skin in one of my devices,but we typically use are small particles,
that are grown in the laboratoryso we can have a sense of what they are.
(16:12):
So they're typically some sort of plasticor silica or glass.
We tend to use dustthat is much more precisely manufactured.
So we know exactly what it is that allowsus to better understand what's going on.
So for my last question,I want to ask about the future
and emerging technologies.
Where would you like to see the field goor where do you think it will go?
(16:33):
Well,if we're talking about plasma physics
generally, that's a complicated questionbecause plasmas are very broad.
So if we think about the plasma physicsportfolio that we have here at the NSF,
we support low temperature plasmas,the types of things that I do.
And on that sidethere's lots of open questions.
What is the charge on the dust
(16:54):
that's not fully understood,but it's an important quantity.
We now have the abilityto make very large magnetic fields.
And that's a new knob that we can useto look at the additional behavior.
There's a project at Auburn University,the Magnetized Dusty Plasma Experiment,
built with an MRI award
from the National Science Foundationjust over ten years ago.
(17:15):
That's a new knobthat allows us to look at things
as we think about going to the moonand Mars.
Well, dust contamination is a real issue.
So being able to controlthe dust is important.
I think there are lots of sortof interesting questions there,
but that's just a small piece.
You have high intensity laserswhere you use lasers
to dolots of really interesting plasma physics.
(17:38):
There's the Zeus facility at Universityof Michigan that is now operational.
They just it 2 petawatt,so the highest power laser in the US,
you can use that to accelerate particles.
So that would enable the next generationof particle physics experiments.
But there's a lot of medical applicationsfor that as well.
(17:58):
You can createextreme environments relevant
to what's happening inside of starsand inside of planets.
Huge parameter space to look at there.
There's currently a design projectto try and push the frontiers further.
That's the NSF OPAL project,which is at the University of Rochester.
That's a three year award that at the end,
they'll have basically a planto build the next generation.
(18:20):
If that were to be funded,
instead of having,Zeus will be three petawatts fairly soon.
This would be a two 25 petawatt beams.
And that would allow us to do thingslike boil the vacuum to create particles
out of nothing, which is just.
Cool stuff Starts to get to whereit's like, what is that?
So if you think about fusion,that's another example of plasmas.
(18:41):
And, you know,there's a lot of questions there.
How does the plasmainteract with the wall?
Is NSF going to fund a.
We're going to build a fusion reactor, no, but are we going to address questions
that are relevant to fusion? Absolutely,right?
Might do the science.That gets us there. Exactly.
But plasma physics isn'tjust in the division of physics,
which is where I sit,you've got GEO space, right?
(19:04):
And in there they look at,you know, the sun and earth
and that connection, as wellas what happens inside the atmosphere.
A lot of plasma physics there.
Space weather. Right?
We've got lots of satellites being ableto understand that and predict that.
That's a big area where I think there'slots of opportunity in engineering.
There's a lot of plasma physicsthat's supported there, in manufacturing
(19:28):
and just trying to understandthe engineering processes.
So there's additional plasma physicsthere.
You know, if you think about semiconductormanufacturing, I think that there's
a lot of exciting possibilities,you know, that's going to be driven by
market needs and then regulationand those, those are hard to predict.
But I think the one thingthat is safe to say is that we are going
(19:49):
to want things that are fasterand more energy efficient,
and there's a lot of questionsthat come in there, right?
I could see lots of interesting examplesof artificial intelligence, right?
When a lot of thesesemiconductors are made,
they come up with whatyou might call recipes, right?
I want this power at this frequency
for this longwith these different conditions, because
(20:11):
that's going to get the plasma closeto sort of making what you want.
The reality is, when you're doing that,there are lots of knobs
that you have to turn,and those knobs have lots of settings
which make it impossibleto find the optimal one.
But you can run several case scenarios,and then maybe you could use machine
learning to say, here's
our input set, here's what the outputis, here's what we really want.
(20:35):
What's the optimal setting.
So you can really sort of fine tune that.
You can do these digital twinswhere you make
a digital replicaof the semiconductor device.
And we've just awarded something wherethey're helping to develop these models
that will allow sort of full scalemodeling of the system
to really understand what's happening,to sort of help drive that process of fine
(20:56):
tuning things, to really
get the right type of environment,to make the kinds of things that you want.
So I think there's lots of excitingopportunities just depends on
sort of what you mean by plasmas,because plasmas really are broad.
Special thanks to Jeremiah Williams.
For The DiscoveryFiles, I'm Nate Pottker. Watch video
versions of these conversations on our@NSFscience YouTube channel.
Please subscribe wherever you get podcastsand if you like our program,
(21:17):
share it with a friendand consider leaving a review.
Discover how the U.S.
National Science Foundationis advancing research at nsf.gov.
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