Since ulrahigh frequency (UHF) plasma has a low electron temperature (less than 2 eV) and uniform density, the effects of electron confinement due to the sheath potential barrier or the plasma potential distributions are less prominent than with electron cyclotron resonance plasma or inductive coupled plasma. Consequently, with no magnetic fields, the pulsed UHF plasma discharge cannot be maintained. To confine electrons at the afterglow in the pulsed UHF plasma, multiplehyphen;cusp magnetic fields are required on the chamber wall. Under this condition, the pulsed UHF plasma can be maintained even at a pulse interval of 40 mgr;s and can significantly improve the etching rate and etching selectivity. That is, electron confinement with magnetic fields plays a very important role for the generation of negative ions at the afterglow in a pulsehyphen;timehyphen;modulated plasma. copy;1996 American Institute of Physics.
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