Production and control of large diameter surface wave plasmas

A planar cylindrical plasma has been produced using small slot antennas in an aluminum discharge chamber with a cylindrical section with a diameter of 22 cm. The 2.45 GHz microwave with a power of 0.2-2.0 kW was fed through a quartz window into the discharge chamber filled with Ar or at a pressure of a few mTorr to 1 Torr. At relatively high pressures, interesting mode patterns of optical emission and microwave field intensity, that is, the TM mode at 1 Torr and TM mode at 0.3 Torr, were observed just below a quartz window. From theoretical analysis, these modes are considered to be attributable to the surface waves excited in a large planar cylindrical plasma. Surface wave plasmas filled with a low-pressure Ar or gas, say 10 mTorr, were also studied for the etching application. Furthermore, we have carried out time- and space-resolved measurements of plasma parameters and microwave field intensity using a pulse-modulated microwave source to study the power absorption mechanism in the surface wave plasma and to demonstrate the pulse-modulated surface wave plasma. Preliminary results also show that short-wavelength fluctuations in the electric field intensity, which might be considered as mode-converted electron plasma waves, exist near the quartz window mm) for 5-10 s after the microwave pulse was applied. Lastly, a recent result of minimizing a dielectric window is briefly presented.