Development of a slot-excited planar microwave discharge device for uniform plasma processing

Summary form only given, as follows. In so-called surface-wave excited plasmas, where the wave is propagating between the slot plate of a few apertures and the plasma surface forming standing wave eigenmodes, produced plasmas are not uniform reflecting the eigenmode patterns and exhibit abrupt changes in density when changing the incident power due to the discrete nature of eigenmodes. We are developing a planar microwave discharge device, where the microwave field is radiated uniformly from the antenna of multiple slots and is strongly damped in the plasma, via resonant absorption, within a short distance. In this case, the plasma is almost free from eigenmodes allowing uniform and stable plasma production. Furthermore, the microwave fields from the slots are rotating in the azimuthal direction, and smooth out azimuthal inhomogeneity, if any. We have developed a 3D finite difference time domain code that calculates wave propagation in nonuniform plasmas. The enhancement of the microwave fields near the plasma resonance is revealed in the calculation in accordance with the theory of the resonant absorption. The global wave electric field is obtained for various excitation modes. In the experiment, the wave field in the plasma is measured by a small antenna to find that it is rotating in the azimuthal direction. The measured wave field patterns are in good agreement with the calculation results.