Production of Large-Diameter Microwave Plasma with a High-Permittivity Material Window

As a large-diameter plasma generation method for ultralarge-scale integrated (ULSI) circuit processes, microwave plasma production was studied by employing a high-permittivity material window. The plasma parameters were examined in conjunction with the permittivity of the dielectric window material. The results revealed that the alumina window with higher permittivity provided higher electron density in both Ar and O2 plasmas. Since this dependence was only seen in the regime above the cut-off density of 2.45 GHz microwave, it was concluded that the plasma production was due to the surface-wave mode. The method was emphasized to be promising in producing a large-diameter plasma for ULSI processes.