Permanent-magnet helicon sources and arrays: A new type of rf plasma

Helicon discharges are known for their ability to produce high densities of partially ionized plasma, their efficiency arising from an unusual mechanism of rf coupling. However, the requirement of a dc magnetic field has prevented their wide acceptance in industry. The use of permanent magnets greatly simplifies helicon sources, and arrays of small sources extend the use of helicons to the processing of large substrates. An eight-tube array was designed and constructed, and its density uniformity measured in a 53×165 cm2 chamber. Three innovations involved (a) the remote field of ring magnets, (b) a low-field density peak, and (c) rf power distribution. High-density plasmas uniform over large areas requires compatibility in all three areas.