In the last few videos we talked
about how desperately the semiconductor industry needs EUV
to cut down the cost associated with
the, each of the lithography and patterning steps.
And we also talked about how challenging this is.
There are lot of challenges in the EUV source in the optics and so on.
So, what I want to talk about in this video is, what if EUV,
EUV lithography doesn't happen? So, what is our Plan B?
So are there a next set of next
generation of lithography techniques that we are looking at?
So this chart over here describes the ITRS
road map for lithography from the year 2011.
Where does it it list out the different lithography options
at each technology node. So we notice that at 45 and 32,
we were, we basically got around by using 193 immersion lithography.
Then we switch to double patterning. Going forward, it says you need EUV.
So EUV is a constant in all going forward.
But what if it doesn't happen?
So it list out the multiple options over here.
So, I want to describe
in these in this video, what these other options are.
And you can see that the, at 11 nanometer, even lists out innovation.
And you really know that you are in big trouble if your roadmap says innovation.
So what are the other, other, other techniques available to us
that we can we can bank on if EUV doesn't happen?
So what I want to describe in this video are
three of these techniques. So the first thing I want to talk to you
about is listed over here which is imprint or Nano-Imprint Lithography.
The second technique that I want to describe to you
is called DSA, which stands for Directed Self Assembly.
And I'll talk to you what it means. The,
finally, the last technique that I want to talk to you about is what is noted over
here as ML2 or Mask Less Lithography or we can all also say Ebeam Lithography.
So let's start with the Nano-Imprint first.
So what Nano-Imprint entails, is described in, very nicely in this chart.
So what it then says is you you spray your wafer,
so you take your wafer and spray it with the, with resist.
And you come on from the top using the stencil or using this
template, which has your feature already patterned into
it. And you press this press this
template on top of your resist, which is a liquid face.
So this, you you pattern your, whatever feature you
want on this liquid resist, and then you do a UV cure.
And so that pattern is baked into your resist and then you remove this template.
And the pattern is essentially embossed into your resist.
So, this says I'm taking this image from this company called Molecular Imprints.
So it was a company based, it's a company based out in Austin.
it started out from UT Austin which developed
this technique and is now trying to commercialize it.
So when looking at it, you, you know, think that
you know, what's new, it, it looks very much like a
embossing
people back in the 15th century or the 16th century,
they used to use the same techniques to print coins.
so what's, what's new I mean it's the same technique the only thing
is it works even better if you if you take it to a nanoscale.
So why's that?
So it works even better at a nanoscale because you have
these capillary forces which assist in this Nano-Imprint Lithography.
So say, you have a big feature, you have a micron sized feature,
you will get limited capillary action which
is pushing your resist into this template.
When you have a small template and you have these features which are
of the order of a few nanometers, you get an even higher capillary action.
So remember capillary action depends it's inversely
proportional of the size of the feature.
So it it's a beautiful technique.
It works even better at smaller feature. Of course, there is no free lunch
in semiconductor industry. So how does this Nano-Imprint Lithography
stack up in these different parameters that
we used to judge any lithography solution?
So on the on, if you look at
the score card, it's actually very good for resolution.
It can essentially whatever resolution you can achieve
on the template, you can exactly achieve it
on your resist, in terms of CD uniformity,
line width roughness, again best in the class.
but the main problem, the main killer for Nano-Imprint Lithography is defects.
So, whenever there's a defect in the template
and it's a very easy that you might get
one or two defects in the template it essentially
balloons up and it creates more and more defects.
First of all, it creates defect, the same defect
in every wafer and then it balloons up and creates
more and more defects.
So that's, that's one of the
main challenges with this Nano-Imprint Lithography.