Characteristics of a microwave electron cyclotron resonance plasma source

The description and performance characteristics of a microwave electron cyclotron resonance (ECR) overdense plasma source are presented. The discharge was generated by introducing the circular TE11 mode wave at a frequency of 2.45 GHz into a cylindrical cavity, which is inmersed in an external static magnetic field from three solenoid coils. For magnetic field values corresponding to the ECR condition, and at pressures 10−4–10−2 Torr, in argon and methane the plasma initiation occurred with 10 W of incident power. The plasma density and temperature were measured using electric probes, and their dependence on the pressure and magnetic field are shown. Optical emission spectroscopy was carried out to identify chemically active species in the plasma. It was found that a high microwave power absorption level could be achieved by reducing the external magnetic field to values near half the resonant one, giving as result the production of a plasma with a density greater than the critical one (overdense plasma).