LONG PLASMA GENERATION USING MICROWAVE SLOT ANTENNAS ON A RECTANGULAR WAVE-GUIDE

30-cm-class long plasmas were generated using 2.45-GHz microwave slot antennas on a rectangular waveguide with a T-shaped ridge for the development of high performance ion sources or for plasma reactors for large-area material processing. The microwave coupling efficiencies above 85% were achieved for Ar, N2, and O2 over large flow rate ranges. From the electric fields on the inner wall E side of the waveguide, standing waves with the maximum electric field strength of about 30 kV/m were expected to be excited in the waveguide, depending on the location of the T-shaped ridge. The plasma density for Ar was in the order of 10(17) m-3 and for N2 and O2 10(16) m-3 in a discharge chamber in front of the slot antennas. The electron temperature for Ar ranged from 3 to 4 eV and for N2 and O2 from 3 to 8 eV. The spatial profiles of the ion saturation current for Ar were almost flat in the discharge chamber although the profiles for N2 and O2, with large flow rates or near the antennas, were slightly rough.