Electromagnetic field characteristics of radial line slot antennas for surface wave coupled plasma production

In plasma processing systems for large sized wafer, quick evacuation of reaction gas by making the process space gap narrow is required to realize higher productivity and better quality of microelectronic devices. The wafer must be placed closely 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, which consists of densely arrayed transverse slots, was fabricated and tested. A uniform, high electron density of 3/spl times/10/sup 11/ cm/sup -3/ and large-area plasma under the condition of low electron temperature has already been realized by experiments. It dispenses with DC magnetic fields required in ECR systems. For further development of slot design as well as the mechanism extraction of plasma generation, this paper evaluates the electromagnetic near fields of SWP RLSAs. As the first step, antennas in free space without the plasma as well as the glass vacuum window, is analyzed using the periodic array model. The predicted near field distribution is compared with the experiments and reasonable agreement is reported.