Radio frequency hollow cathodes for the plasma processing technology

The present paper summarizes the main features of the hollow cathode discharges generated by a radio frequency (r.f.) instead of a d.c. held. The pressure of gas inside the hollow cathode is almost independent on the reactor pressure, which allows to generate discharge at high collision frequency and transport it into the low pressure reactor. The discharge forced out from the hollow cathode forms a decaying plasma channel with extraordinary properties. Gas metastables excited inside the cathode can act in selected gas mixtures as a source of additional heat, thereby enhancing thermionic electron emission and ionization of the gas. An are regime can be started from the glow discharge simply by increasing the r.f. power. Hollow cathode are in the cathode metal vapor can be sustained even without working gas. Examples of utilization of hollow cathodes in the film deposition and dry etching technology are presented. Small size cylindrical r.f. cathodes allow special applications inside narrow (<10 mm in diameter) tubes. Linear are discharge (LAD) magnetrons.