Effect of excitation frequency on the spatial distributions of a surface wave plasma

Using different frequencies of 2.45 GHz and 915 MHz, the effect of excitation frequency on the spatial distributions of a surface wave plasma for 450mm wafer processing was experimentally investigated at a medium pressure of 1 Torr. As a result, it was found that the mode number of standing waves which the surface waves form in the radial direction has great influence on the radial distribution of plasma density. Consequently, the plasma uniformity in the downstream region at 915 MHz was better than that at 2.45 GHz. On the other hand, the electron temperature was roughly constant and below 1.5 eV except in the vicinity of the quartz window at both frequencies.