Coupling efficiency studies of inductively coupled radio frequency plasma

Abstract

A plasma generation system driven by a 13.5 MHz radio frequency (RF) power source was designed and tested. Inductive coupling of the power source to the gas discharge was achieved using different turns of a 4-mm diameter copper tube spirally wound around a cylindrical quartz chamber to serve as the antenna. The 3-turn and 4-turn antenna configurations exhibited low system reflectance down to 10% for RF input powers above 100 W. The produced plasma was investigated using optical emission spectral lines from different species in the discharge. Analyses of the line intensity ratios of Ar⁺ (434.81 nm) and Ar (420.07 nm) revealed that the 4-turn antenna produced electrons with high mean energy compared to a 3-turn antenna. Also, at low gas pressures, the 4-turn antenna system produced a more homogeneous discharge than that of the 3-turn antenna system.