Ionic species in 13.56 MHz discharges in CF4 gas and mixtures of it with Ar and O-2

Signal intensities of positive ions were measured in situ by direct sampling from parallel-plate discharges in CF4/Ar and CF4/O-2 mixtures using a quadrupole mass spectrometer. Major positive ions in CF4/Ar discharge are CFx+ (x = 3, 2, 1) and Ar+. Some of the production of CF2+ and CF+ is considered to be due to the contribution of Ar+. Major positive ions in CF4/O-2 discharge are CF3+, O-y(+) and F-y(+) (y = 2, 1). The signal intensity of CO2+ is of the same order as that of F-y(+). The signal intensities of F-y(+) and O+ in CF4/O-2 discharge are higher than those in pure CF4 and O-2 discharges, respectively. Intensity ratios of the ions vary with the gas mixing ratios.