Inside Multibeam E-beam Lithography
One-on-one: David Lam sounds
off on next-generation lithography and how
to solve some very difficult problems.
BY: MARK LAPEDUS
NOVEMBER 19TH, 2015
Semiconductor Engineering sat
down with David Lam, chairman of Multibeam,
a developer of multi-beam e-beam tools for
direct-write lithography applications. Lam
is also a venture capitalist. He founded Lam
Research in 1980, but left as an employee in
1985. What follows are excerpts of that
SE: How has the equipment
business changed over the years and whatís
the state of the industry today?
Itís a very challenging environment. The
customer base is consolidating. I still
remember the days when there were a lot of
fabs around Silicon Valley in the 1980s.
Back then, there were more companies. You
could approach them with a new technology.
They didnít have to be the biggest company.
But they were willing to be the first one to
try something out. That was a big deal. So
you could really figure out how to improve
your technology. Today, however, the
industry has become extraordinarily
SE: Letís go back in time. In
2009, you stepped in and took over Multibeam.
At the time, multi-beam e-beam technology in
general was (and still is in many cases)
being touted as a next-generation
lithography (NGL). Like EUV, multi-beam was
supposed to pattern all layers and displace
optical lithography. What did you discover
about the multi-beam e-beam market when you
took over Multibeam?
At the time, we recognized that the
multi-beam e-beam market was not there. So,
we needed to understand exactly where the
industry was going and what does the
customer need. Then I saw three developments
in the industry. The first one was DFM. Back
in 2010, every conference was full of DFM
papers. In many cases, the papers discussed
2D layouts. In some cases, people said: Ď2D
layouts are not manufacturable.í Still
others said: ĎOf course you can do that, but
at a higher cost.í In any case, at around
that time, Intel was quietly using 1D
layouts. They were using 1D since 2007. They
switched from so-called 2D, or
two-dimensional layouts, to 1D or lines and
SE: What else did you
The second observation was that optical
lithography is doing both the lines and
cuts. Even today, everybody is using optical
to print their lines and optical to make
their cuts. But here lies a problem. For
printing lines, optical cannot go below
80nm. Optical lithography is dictated by
Rayleighís Equation. But the industry is
smart. It figured a way to get around these
limits with pitch-division. Some people call
SAQP. Itís double- or quadruple-patterning
by using deposition and etch to reduce the
pitch and increase the line density. Itís
cost-effective and everyone has been using
it for the last few years.
SE: So whatís the problem?
You can use optical for the lines. But how
about the line cuts? You have to resort to multiple
patterning today. Multiple
patterning is the default solution. So now,
everybody is screaming about cost. Not about
the lines, even though you need multiple
steps like pitch-division with deposition
and etch. That cost is acceptable. The issue
involves line cuts and holes, where you need
to use optical with multi-patterning. All
the cost comes from there.
SE: What was the third
At SPIE in 2010, Yan Borodovsky of Intel
presented a famous paper on complementary
lithography. (Borodovsky, a former fellow at
Intel, retired from the company earlier this
year). If I were to paraphrase Borodovskyís
presentation, he said: ĎDonít get hung up on
NGL. It doesnít have to be one single
lithography technology to do the work. There
could be two lithography technologies that
work hand-in-hand to solve the patterning
problems for the critical layers and to
reduce cost.í What Borodovsky meant by the
critical layers are the line-cut layers and
SE: Based on those
observations, it appears that Multibeam
started to develop a multi-beam e-beam
technology called Complementary E-Beam
Lithography (CEBL). CEBL is aimed for
direct-write lithography applications. So
where does CEBL exactly fit in?
If we are able to take multi-beam e-beam
technology, and handle just the cuts, then
we have an opportunity to contribute to the
solution. So we are not an NGL, but rather
we are a complementary technology.
SE: So in a nutshell, CEBL is
not focusing on the lines. It is focusing on
the cuts only, right?
Yes. We are not trying to replace optical.
We want to support the extension of optical.
Optical lithography is doing a great job in
printing lines and doing the front-end.
SE: Whatís the current status
of your product?
I canít talk about those things. Itís at the
SE: In general, though,
multi-beam e-beam technology is well
understood. It uses multiple e-beams to
print patterns directly on a wafer. The big
advantage of direct-write is that it does
not require a costly photomask. When CEBL is
introduced into the market, what will it
bring to the party?
At one time, I envisioned that the industry
would be moving toward a number of new and
diverse applications. So the industry would
have to do a lot of prototyping of chips. In
a recent presentation, I discussed how CEBL
can help the industry reduce the cost of
prototyping. The design changes that you
need to make in prototyping today require
you to get a new set of masks before you do
a re-spin. One mask-set is very costly. It
takes six weeks or something like that. Now,
with CEBL, designers can input the data, and
make changes, into the computer directly. So
weíre talking about reducing the weeks to
hours. The cycle time and cost will be
SE: In the past, youíve
talked a little about your product. Is it
still based on a multi-column approach?
Yes. The first thing we did was to
miniaturize the columns. Now, you can have
an array. Then, you can do parallel writing.
You have to make the columns smaller in
order to have multiple columns. If the
columns are bigger, you have a magnetic
field. Then, you need a magnetic core to
generate the field. Thatís a large system.
What we did was to get rid of the magnetic
field. Everything is electrostatic.
SE: What else?
We can take full advantage of 1D layouts. We
focus on the cuts. If you do the cuts and
add the total area, itís about 5% of the
wafer. So essentially, you deflect the beam
towards the cuts. And you skip 95% of the
rest of the wafer.
SE: Can you say anything more
about your system?
We designed our column with a relatively
high current. You also need a scalable
architecture. We have a single module that
works. We are also developing a cluster tool
with multiple modules. You can start
prototyping using one single module. You
wonít need more than that to develop the new
chip. But after that, every module is copy
exact. So with multiple modules, you can
transition from prototyping to volume
production very fast.
SE: Still, there is a lot of
skepticism about direct-write and multi-beam
e-beam for lithography. In the 1980s, IBM
tried and failed with direct-write e-beam.
Others have promised the technology, but
failed to deliver. Any comments?
There has been skepticism for a long time.
When I first took over the company, I tried
to explain what we do. The industry said:
ĎIf IBM couldnít do it, then why do you
think you can?í At the time, I didnít have
an answer to that. The second question
people asked was this: ĎIf you think e-beam
is so good, where have you been for the last
SE: There are other issues.
Over the years, e-beam and multi-beam for
direct-write lithography have never gained
much traction. Why?
Tennantís Law essentially captures in a
single equation the difficulties of e-beam
direct-writing getting into the mainstream.
Tennantís Law can be represented by T=k R to
the fifth power. T is throughput, k is a
constant and R is resolution. Tennantís Law
shows that throughput for direct-write
lithography deteriorates rapidly with
improving resolution. When feature size
improves by 50%, throughput drops to 3%.
Thatís why e-beam direct-write has so many
problems and never got into mainstream
SE: How do you answer the
skeptics? And how is your approach different
The key is that we are not falling into the
same trap as the conventional e-beam
approach. The conventional e-beam approach
is a single column with pixel writing.
SE: Multibeam appears to have
found the right formula and is making
I can tell you this. Itís coming along very
well. We have customers.
About Multibeam Corporation
Multibeam Corporation is a leading innovator of
electron-beam direct-write technologies that aim to
dramatically reduce lithography costs in the
manufacture of advanced ICs. With more than 30
patents filed and issued, the Silicon Valley
pacesetter develops Complementary E-Beam Lithography
(CEBL) systems that seamlessly work with
state-of-the-art 193nm immersion (193i) optical
lithography systems. Fully leveraging existing
industry infrastructure, Multibeamís CEBL promises
to reduce both production costs and cycle times
while improving yields by eliminating the need for
optical multi-patterning of critical layers in
For advanced nodes, leading IC
companies have shifted from random 2-directional
layouts to the regular 1D lines-and-cuts style.
Today, 193i systems print the lines effectively but
require 2, 3, or even 4 litho-etch passes to print
the cuts and holes in one critical layer. This
complicated process, known as multi-patterning,
drives up mask cost, capital cost, and cycle time.
CEBL is an ideal solution to stem this escalating
cost. In the hybrid mode, Multibeam CEBL complements
193i by directly patterning cuts and holes with no
masks, thus eliminating the soaring costs associated
ramifications of optical multi-patterning are severe
and extend beyond mask-and-tool costs.
Multi-patterning also negatively impacts yield due
to increased errors in critical dimension and
overlay, as well as rising defects. As a complement
to 193i lithography and established pitch-division
techniques, Multibeamís CEBL promises to change the
manufacturing game for patterning critical layers.
Based in Santa Clara, California, Multibeam is led
by Dr. David K. Lam, the founder and first CEO of
Lam Research who successfully guided the development
and market penetration of his eponymous companyís
first fully automated plasma etch system. Widely
recognized as a key contributor to the growth of the
semiconductor industry, Dr. Lam was inducted into
the Silicon Valley Engineering Hall of Fame in 2013.
Media Contact: Tom Rigoli,
Vice President, Multibeam
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