Scaling of microwave slot antenna (SLAN): A concept for efficient plasma generation

In slot antenna (SLAN) type plasma sources the microwave power is coupled from an annual waveguide (ring cavity) through equidistantly positioned resonant coupling slots into the plasma chamber made of quartz. The symmetrical power distribution and the surface wave at the plasma-quartz interface allows large-area plasma generation. Three plasma sources with 4, 16 and 66 cm quartz tube diameter (ring cavities with 4, 10 and 30 coupling slots respectively) are compared. The ECR versions of them are also considered. The ignition performance and operation pressure range are presented. Plasma parameters (ion concentration, electron temperature) and their radial and axial distributions are shown. The computation tools used for the design of sources with different dimensions are described. The scaling rules and limitations of up-scaling are discussed. These are plasma inhomogeneity due to diffusion and recombination processes, thermal load of the microwave components, and thermal and mechanical load of the plasma chamber and substrates. The up-scaled discharge architecture for remote processing, suppressing the direct microwave heating and ion bombardment is proposed.