Production of inductively-coupled large-diameter plasmas with internal antenna

Large-diameter RF plasmas at 13.56 MHz have been produced by inductive coupling of an internal-type antenna in a discharge chamber of 400 mm diameter and 200 mm height. For minimization of the electrostatic coupling, (i) a double half-loop antenna of 360 mm diameter was employed for the reduction of antenna inductance and (ii) the antenna conductor was terminated by the insertion of a blocking capacitor to satisfy the impedance balance condition where the RF-voltage amplitude could be minimized to 1/2 the terminal voltage. The plasma source could be operated stably at RF input powers of up to 3 kW to attain plasma densities as high as 1012 cm-3 at Ar pressures around 1 Pa. Furthermore, (iii) full covering of the antenna conductor with an insulator tubing exhibited a significant effect on the suppression of the electrostatic coupling with simultaneous achievement of plasma densities as high as 5 × 1011 cm-3.