A Helicon Plasma Source for Large-area Materials Processing

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A Helicon Plasma Source for Large-area Materials
Processing DMI-0115570 Francis F. Chen, UCLA
Part 4 Applications
Part 1 Proof of Concept
Part 3 Planned Innovations
Part 2 Why Helicons?
A. Dry processing of flat panel displays e.g.
etching of ITO and aluminum. Also, deposition of
SiO2 on plastic for flexible displays.
Medusa
Helicon sources produce much higher density at
the same power as other commercial sources.
An arbitrarily large array of individual sources
can be made to cover large substrates uniformly.
This is easier if permanent magnets can be used.
Though ideal for semiconductor processing, that
industry currently has large enough sources.
A. Optimization of source type and size antenna
type magnetic field coils, and source spacing.
In Greek mythology, Medusa was a monster who was
so ugly that a single glance at her would turn
you into stone. She had a tangle of snakes for
hair. Our first experiment with multiple
helicon sources looked like a Medusa, with its
cables distributing the RF power to each tube.
This was a previous project.
They do this with antennas that generate a
helicon wave IN A DC MAGNETIC FIELD. This wave
then couples to a cyclotron wave on the outside,
and it is THIS wave that is absorbed very
efficiently.
B. Web coating of plastic or glass sheet, for
instance for paint adhesion or water repellency.
Permanent magnets.
B. Replace coils with permanent magnets
There are TWO kinds of helicon discharges the
BIG BLUE MODE (left), and the LOW-FIELD PEAK
(right). At high fields, the BLUE mode gives very
high density, fully ionized, in a narrow core.
At low fields, a more uniform, lower density,
more useful plasma is created.
Single Tube Test Stand
At 7 cm below the sources, a uniform plasma is
achieved over a 400 mm diameter without
optimization of the array. With 3kW of RF power,
the plasma density approaches 2 ? 1012 cm-3.
This has been constructed and is operating
Azimuthal scans show no evidence of m 6
asymmetry due to the individual sources. The
uniformity over a 400-mm diam circle is /- 3.
This shows that an array of helicon sources can
produce dense plasma efficiently over arbitrarily
large areas.
C. The BIG BLUE MODE can be used to produce
intense, focused ion beams for machining of
nanostructures.
The L.F. density peak occurs at economical
fields. It is caused by constructive
interference of the wave.reflected from the
endplate.
First light!