1. DMI-0115570: Francis F. Chen, UCLA
A Helicon Plasma Source for Large-area Materials Processing
DMI : 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!