Ashing Properties in a Surface-Wave Mode Plasma with a High-Permittivity Alumina Window

Ashing properties in a surface-wave mode at 133 Pa and 1 kW with an alumina disk-plate window are investigated by comparison of those in a volume mode with a quartz disk-plate window. In the surface-wave mode, plasma is confined to the alumina window surface area and ashing in a downstream area is carried out mainly by atomic oxygen. The ashing activation energy of 0.42 eV in the surface-wave mode ashing is comparable to 0.5 eV with an ashing condition by atomic oxygen at the ground state [O( 3 P)](the so-called downstream state). These results indicate that the plasma in the surface-wave mode can realize a downstream ashing condition. On the other hand, ashing with a quartz window was done by plasma, where the activation energy is influenced by built-in high-frequency magnetic field. Moreover, the ashing rate distribution in the surface-wave mode characterized with the alumina window is more uniform than that in the volume mode with the quartz window.