Positive Ions in C 4F 8 RF Discharge in a Planar Diode

Positive ions were measured in situ by direct sampling from C4F8 discharge at 13.56 MHz using a quadrupole mass spectrometer. Major positive ions in the discharge plasma are CF+, CF2 +, CF3 +, C2F4 +, C2F5 + and C3F5 +. When the gas flow rate increases, the signal intensity of C2F4 + increases. The intensity variation of C3F5 + is similar to that of C2F4 +. However, those of CF3 + and C2F5 + decrease with increasing gas flow rate, and those of CF+ and CF2 + are almost constant. The difference in intensity variations is considered to result from the production processes of ions.