Large volume radio‐frequency plasma source using a magnetic line‐cusp field

A large volume cylindrical radio frequency (rf)‐plasma source with a magnetic line‐cusp field has been developed for large scale plasma processing. In this type of plasma source, a capacity‐coupled 13.56 MHz rf plasma is produced in the presence of a magnetic line‐cusp field. Two versions of the plasma source have been made and tested. The first version has peripheral rf electrodes placed on the outside of the ionization chamber, and is suitable for preparing a large volume uniform plasma. This plasma source can attain a useful area of uniform plasma over a 30‐cm‐diam region within 10% nonuniformity. The second version is featured by parallel doughnut‐plate electrodes which forms part of the chamber wall and serves as a high current source. The electron density in such a version is proportional to the rf power, being equal to 4×1010 cm−3 at 400 W. The measured electron energy distribution function showed the Maxwellian‐like distribution from a drift motion in the magnetic line‐cusp field.