Near-Field Distribution of Radial Line Slot Antenna for Surface-Wave-Coupled Plasma Generation

In plasma processing systems for large-size wafers, quick evacuation of reaction gas by making the process space narrow is urgently required to realize higher productivity and better quality for microelectronic devices. Wafers must be placed close to the antenna aperture in this case. A radial line slot antenna (RLSA) for surface-wave-coupled plasma (SWP) is a promising candidate to this end. A novel slot arrangement in the aperture, consisting of densely arrayed transverse slots, was fabricated and tested. A uniform, high-density (3 x 10(11) cm(-3)) and large-area plasma at low electron temperature has already been realized in previous experiments. It dispenses with the DC magnetic fields required in ECR systems. For further development of the slot design, as well as the mechanism determination of plasma generation, in this paper we evaluate the electromagnetic near fields of SWP-RLSAs. As the first step, antennas in free space without the plasma as well as a glass vacuum window, are analyzed using a periodic array model. The predicted near-field distribution is compared with those of previous experiments and a reasonable agreement is reported.