Projection optics for the coating deposition system that the team
co-developed with private industry.
microprocessor technology developed by Lawrence Livermore and Veeco
Instruments Inc. could increase the speed of personal computers
by 10- to 20-fold and their memory capacity by 100- to 1,000-fold.
The Production-Scale Thin-Film Coating Tool is a highly precise
deposition system that opens the door to advanced, high-volume manufacturing
of the next generation of microprocessors. It is one of this years
R&D 100 Award winners.
the new technology, powerful desktop computers could be made that
realize a wealth of exciting applications, including real-time multilanguage
voice recognition, translation, and human interfaces. Applications
such as these are impossible on todays 1-gigahertz PCs,
says Regina Soufli, Livermore physicist and leader of the team that
developed the coating tool. Technology enabled by the tool
will allow tomorrows PCs to approach the computing power of
todays multimillion-dollar mainframe systems that presently
only exist in laboratories.
|Members of the Livermore team
are, from left, Jim Folta, Rick Levesque, Claude Montcalm, Swie-In
Tan, Mark Schmidt, Regina Soufli, Fred Grabner, Chris Walton,
and Eberhard Spiller. Missing from the photo is Steve Vernon.
Radiation at the extreme ultraviolet wavelengths
is strongly absorbed by matter such as air or the lens material.
For this reason, the entire EUVL system has to be maintained under
a vacuum, and the light that produces the circuit image must be
reflected from mirrors rather than refracted through lenses. Furthermore,
the mirrors must consist of precisely figured glass substrates that
have been coated with alternating layers of molybdenum and silicon
to a thickness of 280 nanometers. This thickness can only vary by
less than 0.05 averaged over the entire optical surface; such a
variance is equivalent to one-quarter the diameter of a silicon
If this stringent specification
is not met, the printed circuits will be blurred and will fail.
The challenge of making precision-coated optics and doing so in
a reproducible manner is daunting and thus an obstacle to implementing
EUVL lithographic steppers. There were doubts that such thickness
precision could be achieved repeatably, says Soufli.
A daunting task to be sure,
but Soufli and her team are receiving accolades for accomplishing
it. Built on the basis of Livermores expertise in thin-film
technology, the coating tool can deliver commercial-quality multilayer
coatings on the optics used in the camera and illuminator of EUVL
semiconductor steppers. The tool has achieved the 0.05-nanometer-thickness
precision required on camera optics. As a demonstration of success,
the same optics have also been used to print integrated circuit
patterns as small as 39 nanometers. This is the best imaging resolution
ever achieved with optical lithography and foreshadows the ability
to print circuits at the 30-nanometer resolution required for next-generation
|Process engineer Mark Schmidt
places an optical substrate in the coating deposition chamber.
Way It Works
The new coating tool is based
on the magnetron sputtering method widely used for thin-film deposition.
The coating takes place inside a chamber where molybdenum and silicon
sputter sources have been placed 180 degrees apart. The sources,
called magnetrons, have a magnetic field attached to the back of
their surface. With the chamber maintained under vacuum, the magnetrons
are ignited, and a small amount of argon gas is introduced into
the system. Argon ions, excited by the electromagnetic field, impinge
on the sources and sputter atoms off the two materials. The atoms
land on the optical substrate that sits atop a rotating deposition
platter. The rotating platter passes alternately under the magnetrons,
resulting in alternating layers of the two materials being deposited
onto the optical surface. The platter is rotated under the sources
at speeds of about 1 rotation per minute, while the individual substrates
are simultaneously spinning fast around their centers at several
hundred rotations per minute, thereby equalizing the spatial variations
of the sources.
The tools ability to
control film thickness is based on a simple concept: The speed at
which the optic passes under a sputtering source determines how
much of that sputter material is deposited on the optical surface.
Platter speed is modulated as the substrate passes under the silicon
and molybdenum targets, depending on what thickness profile is desired.
The most critical step of
the entire process is determining the right coating recipe for a
given optic, and this is done with the help of computer simulation.
First, using the substrate shape and desired coating thickness profile
as input, a custom-designed computer model simulates the deposition
process. The algorithm calculates the platter velocities and angles
that should be applied and proposes a coating recipe that is tested
on a surrogate optic. The resulting coating thickness on the surrogate
optic is measured, compared with the desired profile, and fed back
to the algorithm to adjust the recipe. The final recipe is arrived
at after four or five iterations of simulation and adjustment. When
put into use, the recipe must be calibrated only once for each set
of optics and is stable enough to be repeatedly used for over a
The new coating deposition
system can produce multiple sets of optics in a high-volume production
mode with precisely identical thickness profile. This way of controlling
coating thickness is accurate, quick, and inexpensive.
the Wave of the Future
coating tool represents a breakthrough in semiconductor equipment
manufacturing. It enables the commercialization of EUVL. Beyond
EUVL, the tools capabilities can be applied in other areas
where thin films with precision thickness control are needed, such
as astrophysics, magnetics, and biological x-ray imaging.
We achieved commercial-level
thickness control for the first time ever on large multilayer optics,
says Soufli. By implementing a versatile design and a unique
deposition algorithm, the tool has enabled commercialization of
EUVL as the next-generation technology for highly advanced computers
of the future. The first EUVL-fabricated computer chips are
scheduled to be developed in 2007. Expect to be able to buy your
very own supercomputer shortly thereafter.
Key Words: extreme
ultraviolet lithography (EUVL), magnetron sputtering deposition,
production-scale thin-film coating tool,
R&D 100 Award, semiconductor computer chips.
For further information contact Regina Soufli (925) 422-6013 (firstname.lastname@example.org).