EFFECTS OF THE AXIAL EXTERNAL MAGNETIC-FIELD ON THE REDUCTION OF THE DIELECTRIC WINDOW DAMAGE DUE TO CAPACITIVE COUPLING IN THE INDUCTIVELY-COUPLED PLASMA

The degree of the capacitive coupling in the radio frequency inductive ly coupled plasma was estimated by measuring the de shift of the poten tial at the central inner side of the dielectric window. Its value was -82.2 V for the condition examined (1.1 kW, 1.5 mTorr, C4F8 plasma, f low rate 20 seem) and the dielectric window was severely damaged owing to this potential difference from the plasma potential, which could b e confirmed with the quadrupole mass spectrometry. When an axial exter nal magnetic field was applied, the mass spectrometer signals, which i ndicate the damage of the dielectric window, decreased drastically in addition to the improvement of the power transfer efficiency. This was mainly caused by the transition from the etching of the dielectric wi ndow to polymer formation due to the reduced window potential as a res ult of the application of magnetic field. (C) 1997 American Vacuum Soc iety.