A computational investigation of the rf plasma structures and their production efficiency in the frequency range from hf to vhf

The influence of driving frequency on discharge structure and production efficiency has been investigated in Ar over the frequency range from 13.56 MHz to 100 MHz in terms of the relaxation continuum model. Under constant rf voltage, the plasma density increases in proportion to the square of the driving frequency. The net ionization and excitation rates, and the power density, show the same frequency dependence, although the collisional production efficiency per input power density is almost invariant with change of frequency. This has the great advantage for plasma processing and deposition from plasmas that parallel plate discharge in very high frequency (vhf) will lead to the system being rather free from ion damage or effects of confined plasma volume as compared with those in high frequency (hf) and microwave (mw).