Surface wave plasma production employing high-permittivity discharge tube for material processing

As a novel method of plasma production, microwave-sustained discharge was studied, particularly focusing on the permittivity effect on the axial distributions of the plasma in the discharge column with the two discharge tube materials. In the alumina discharge tube with a high permittivity, the axial distribution of electron density showed to be very localized in the upstream, nearby the microwave launcher, while in the quartz with a low permittivity a high er density region appeared further downstream. This difference in the axial distribution of the electron density could be explained by the behavior of the surface wave. It was stressed that this property could be one of the biggest advantages in its application to material processing on the industrial level, particularly in achieving a low-damage plasma process, such as low-damage silicon etching.