Plasma characterization of an electron cyclotron resonance–radio-frequency hybrid plasma reactor

Abstract

Langmuir probe measurements have been carried out for Ar, O2, and CF4 plasmas generated by an electron cyclotron resonance–radio-frequency (ECR–rf) hybrid plasma reactor. The resonance width of electron cyclotron resonance, defined at one-half of the maximum plasma density, is measured to be ∼200 G below 1 mTorr and increases with gas pressure for all three gases. No enhancement in the plasma density was observed in the ECR region at or above 70 mTorr for all three gases. The mean electron energy was measured to be 7.2 eV for a microwave power level of 700 W and the energy distribution is nearly Maxwellian. Plasma density increases with the magnetic field. The magnetic field effect becomes more prominent when rf bias is applied to the substrate electrode. The rf bias not only extracts ions from ECR-generated plasmas, but also generates a plasma more effectively due to the magnetic field.