EMISSION-SPECTROSCOPY AND ACTINOMETRY IN A MAGNETIZED LOW-PRESSURE RADIO-FREQUENCY DISCHARGE

A low pressure 13.56 MHz radio frequency (rf) discharge is generated between two coaxial cylindrical electrodes, and is confined by two different types of magnetic field. A plasma electron temperature Te of typically a few electron volts is estimated from experimental spectroscopic data. Application of a homogeneous magnetic field appears to lower this Te by a few tenths of electron volts. Spatially resolved emission spectroscopy in an argon discharge shows that the magnetic confinement of plasma electrons leads to nonuniform emission intensities. The observed distributions can be related to ion density profiles, which have been measured with a Langmuir probe. It is shown that, at the low gas pressures considered here (several milliTorr), metastable states play an important role in the excitation and ionization mechanisms sustaining the discharge. Both experimental and theoretical arguments are presented to support this view. Actinometric measurement of the relative fluorine density in a magnetized CF4 discharge indicates a high density of fluorine radicals. Only at low pressures an additional increase of the fluorine density is observed for higher magnetic field strengths. © 1990, American Vacuum Society. All rights reserved.