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San Jose, California, April 24 – 28, 2022
(The following diary appeared first as a daily blog at life.lithoguru.com and is reproduced here in a slightly edited form.)
SPIE
Advanced Lithography and Patterning Symposium 2022 – day 0
“The
SPIE Advanced Lithography conference begins with one word on
everyone’s mind:
coronavirus.” These are
the first words I used in my blog post two years ago, just as the
SPIE Advanced Lithography Symposium of 2020 was about to begin on
February 23. I had no
way of knowing that within three weeks pretty much the whole country
would start locking down.
That 2020 conference went off without any known coronavirus
transmissions, thank goodness, and two+ years later I think that
first sentence applies equally well today.
Last year’s symposium was virtual, and this year’s has been
postponed two months, just long enough to allow the Omicron variant
to fad and for most of us to gather with more confidence.
It's good to be live and in-person!
I’ve already seen on Sunday several folks that I have only
seen on Zoom for the last two years, and it is a great pleasure!
The conference is promising to be a good one, effected though
it is by the lingering impact of the pandemic.
Virtually no one from Taiwan, Korea, or Japan has been able
to attend, and participation from Europe is down significantly.
Still, registration currently sits at 1,300 (as opposed to
the pre-pandemic average of about 2,000), which is better than I was
expecting. There were
390 paper submissions this year (in 2020, the number was about 500)
and I’m hoping for a very good program.
There
have been a couple of major changes in the symposium this year.
The EUV and Optical Lithography conferences have merged (now
called Optical and EUV Nanolithography), reflecting the continued
mainstreaming of EUV lithography out of development and into
semiconductor manufacturing.
The topic of computational lithography, formerly homed in the
Optical Lithography conference, now resides in the refocused DTCO
and Computational Patterning conference.
These are both good changes, and I look forward to seeing how
they play out this week.
SPIE
Advanced Lithography and Patterning Symposium 2022 – day 1
As
always, the opening of the symposium began with some awards.
Our community’s biggest and most prestigious is the Frits
Zernike Award for Microlithography, and it was wonderful to see
Harry Levinson receive this year’s honor.
(Full disclosure – I’m on the award selection committee.)
Additionally, since last year’s award ceremony was virtual,
Bruce Smith was giving his 2021 Frits Zernike Award for
Microlithography as well.
Congratulations to them both!
Four
presentations of SPIE fellow were made next:
Nelson Felix of IBM, Kevin Lucas of Synopsys, Uzodinma
Okoroanyanwu of the University of Massachusetts, and Tatyana Sizyuk
of Argonne National Laboratory.
It’s a shame that Kevin and Uzo could not be here this week.
We next
heard two of the three plenary talks (Eric Hosler’s talk on quantum
computers will be given on Tuesday.)
The first talk was by Luc Van den hove, President and CEO of
imec.
A quick
digression. We have had
over the years a number of plenary talks given by various industry
executives covering topics of interest to our community such as
compute scaling, artificial intelligence, the automotive industry,
progress in GPUs, etc.
My biggest fear for these kinds of speakers is getting what I call
the “kid on a skateboard” talk.
The executive, giving the same talk they might give at an
investor conference, says things like “Technology A is very
important” while showing a kid on a skateboard, “Our company is
ahead on technology B” then shows a family playing with a dog, etc.
Very slick, and devoid of useful content.
So when a CEO is asked to give a talk on a Wall
Street-friendly topic such as “The endless progress of Moore’s Law”,
I usually get worried.
But Luc
Van den hove is not your typical CEO.
He is a lithographer deep in his bones.
He published his first SPIE paper in 1990, and was chairman
of the Optical Microlithography conference in 1998 and 1999.
He knows what he is talking about, and cares deeply about
this community. So when
the first few slides in his talk were of the “kid on a skateboard”
variety, I was not worried.
He soon got into the technical meat of the topic, and we were
all rewarded for our patience.
Taking the broad view of what Moore’s Law means that is
typical of today, he described four general areas that will keep
progress in semiconductors moving for quite some time (though not
the hyperbolic “endless”):
Shrinking the transistor, improving the transistor, moving
into the third dimension, and shifting compute paradigms.
I suspect that he is correct on all counts.
The
second plenary by H.S. Philip Wong of Stanford went into
considerably more detail on two of Luc’s topics, system-level
optimization and 3D integration.
Dr. Wong is an expert on these topics and I learned quite a
bit. He would have been
better off, however, if he had not tried to force lithography
relevance into his talk through his provocative title and subsequent
discussion of EUV lithography throughput (Tony Yen – you were a bad
influence!).
For the
rest of the day I alternated between the metrology conference and
the two keynote talks at the Optical and EUV Nanolithography
conference. Nelson Felix
gave a nice review of metrology needs for nanosheet transistors,
though I was very surprised when he showed that 1/3 of all the
process steps in IBM’s latest generation process were metrology
steps, and that this hasn’t changed since the 45 nm node.
There is no doubt that IBM does more metrology than your
typical fab. Mark
Phillips of Intel gave a very optimistic view of when high-NA EUV
lithography could be inserted into manufacturing, beating by a year
the roadmap shown by Luc Van den hove (which, coming from imec,
could also be assumed to be optimistic).
It sounds to me that Intel is tired of being behind in EUV
and is hoping that high-NA EUV will give them a chance to leapfrog
ahead.
I ended
the day with a Fractilia hospitality event at a favorite San Jose
brew pub. Thanks to all
who joined us!
SPIE
Advanced Lithography and Patterning Symposium 2022 – day 2
The
first talk of the metrology conference on Tuesday was by Andras
Vladac of NIST on a topic I am very interested in – characterizing
the non-ideal behavior of scanning electron microscopes.
His presentation style was somewhat unique:
taking the material from what appeared to be a half-day short
course and presenting it in 20 minutes.
This is a definitely a talk where viewing and studying it
later (thanks to SPIE’s recording) is a must.
The other talks in the SEM session were good as well, but
more digestible.
Tuesday
was packed with customer meetings for me – a mixed blessing.
I missed many good talks, but got to have facetime with
people I had not been able to visit for at least two years.
I managed to catch the end of Erik Hosler’s plenary talk in
the afternoon on “The path to a useful quantum computer”.
One of the more interesting insights was his need to use
state-of-the-art immersion lithography for the fabrication of his
devices, not for the resolution but for the precision of the
manufacturing. For an
optical device, feature sizes are in the hundreds of nanometers or
microns. But quantum
optical devices require on the order of 1 nm line-edge roughness
from those features, which definitely pushes state-of-the-art
capabilities and makes fabrication quite challenging.
SPIE
Advanced Lithography and Patterning Symposium 2022 – day 3
In the
morning, the optical and EUV session included two very good talks on
EUV pellicles. Mark van
de Kerkhof described ASML’s latest material, a composite made of
metal silicide crystals (if I got that right) that performs just a
little bit better than the prior polysilicon-based stack.
At almost 92% transmission (one pass), it is a few percent
better than the previous best and survives up to 400W source power.
Is it good enough to be adopted in manufacturing?
I’m not sure. The
next talk by Lintec described a 95% transmitting carbon nanotube
pellicle, quite a promising result.
Their pellicle is making progress but did not seem
manufacturing ready, requiring a bit more time to mature.
In the
metrology session, my colleagues Gian Lorusso and Mohamed Zidan from
imec gave a pair of good talks on the metrology challenges for
measuring very thin resists.
(Full disclosure – I was a coauthor on both papers.)
When the as-coated resist thickness reaches 10 nm, line/space
patterns have almost no contrast in a SEM, making measurement of CD
and LWR extremely difficult.
Lowering the SEM voltage to 300V, and even lower for some
materials, improved things.
It looks like 15 or 20 nm thickness and above is manageable
with the right SEM measurement conditions.
I was
also very impressed by Nearfield Instruments and their high
throughput AFM, described by Cornel Bozdog.
Using four AFM heads running in parallel they could measure
64 0.5micronX0.5micron regions per wafer and get a throughput of 12
wafers per hour. While
I’m sure the typical “your results may vary” caveat applies, it is
still an order of magnitude faster than I would have expected.
Quite a
few students are attending the conferences this year, and I’ve been
able to meet some of them.
Seeing the look of these eager young people, drinking from
the firehose of information pouring out in each of the sessions,
makes me hopeful for the future of our industry.
SPIE
Advanced Lithography and Patterning Symposium 2022 – day 4
The
mood at the conference this week can be summed up in one word:
happy. We were
all just happy to be here, with smiles visible everywhere, even
under masks.
Thursday morning began with a quite philosophical keynote talk in
the metrology session on the role of MI (metrology and inspection)
in semiconductor manufacturing by Younghoon Sohn of Samsung.
He touched on broad subjects like the role of sampling
(depends on the failure rate), the dilemma between resolution and
speed in inspection (and the wide gulf in both between optical and
e-beam inspection), and the basic roles of MI (define a process
window, identify cause and effect, and process monitoring and
control).
A joint
session between Optical/EUV and Etch provided several nice papers.
Angelique Raley gave an overview of three techniques being
promoted by TEL: a
spin-on SiC underlayer for EUV to prevent pattern collapse, a
development process (not really explained) called ESPERT for Inpria
resists that also prevents pattern collapse by improving the
sidewall profile, and a cryogenic etch for lower LCDU (local
critical dimension uniformity) and defectivity.
Roberto Fallica of imec gave a quote that I like (and often
say myself), “Stochastics is the major roadblock for EUV
Lithography”. He then
talked about a “healing” etch process that reduces contact hole LCDU
through an aspect ratio dependent etch rate (high aspect ratio
resist patterns etch faster, causing narrow holes to widen, while
low aspect ratio resist patterns etch mode slowly, causing wide
holes to narrow). One
interesting (and confusing) result was that the dose that provided
smallest LCDU was not the dose that gave the lowest defectivity.
Finally, Qinghuang Lin of Lam talked about the application of
Lam’s new dry-deposited and dry-developed resist to contact holes (I
was not able to catch Rich Wise’s earlier paper on its application
to lines and spaces).
Since I
left after lunch to catch a plane home, I was not able to see what
I’m sure were some good papers on the last afternoon of the
symposium. After a
valuable and rewarding week here in San Jose, I was still anxious to
get home. Looking back
two years, here is how I ended my
Advanced Lithography Diary in February of 2020:
“The
week has also seen an escalating concern over the new coronavirus,
COVID-19. Like everyone
else I am monitoring developments with morbid fascination, but also
to see how it will impact my immediate future.
And it has. If
there is any positive to the spreading fear over the spreading
virus, it is that I will soon be traveling far less.
I have started asking customers if we could schedule our
meetings, demos, and courses using video conferencing rather than
in-person, and they are readily agreeing.
Maybe such accommodations will be a permanent trend, with the
significant savings in time and resources that come with less travel
(not to mention a better quality of life when I spend more time with
my family). I will look
to this thought as a small consolation.”
That
prediction proved true.
Like everyone, I have spent much of the last two years living
my
life on Zoom. But
since my life before the pandemic involved far too much travel, I am
grateful for the respite that the pandemic forced upon me.
I am very glad to be back at ALP live and in person, and am
glad that I can start visiting customers again (most of them,
anyway). But the
much-accelerated use of video meeting technology has permanently
changed the way I do business, and I am happy for the family time it
will enable. Like most
of us, this pandemic has triggered a reckoning in my life/work
balance, and I am happy for the result.
So, for
those of you who wanted to but could not come to San Jose this week,
I hope to see you next year.
But if not, maybe I’ll see you on Zoom.
Chris Mack is a writer and lithographer in Austin, Texas.
© Copyright 2022, Chris Mack.
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