FLUOROCARBON HIGH-DENSITY PLASMAS .8. STUDY OF THE ION FLUX COMPOSITION AT THE SUBSTRATE IN ELECTRON-CYCLOTRON-RESONANCE ETCHING PROCESSES USING FLUOROCARBON GASES

An important component in the basic chemical and physical mechanisms w hich govern etching and deposition processes in high density plasmas i s the chemical identity and relative fluxes of ionic species at the su bstrate surface. Here we report line of sight measurements of relative ion fluxes made with a quadrupole mass spectrometer through an orific e in the substrate holder of an electron cyclotron resonance reactor c onfigured for fluorine-based etching. The relative ion fluxes versus m icrowave power and pressure for CF4 and CHF3 plasmas have been studied . These data have been compared with Si and SiO2 etch rates to determi ne the effect of ion flux composition changes on etching processes. It was observed that the F+ ion flux increases relative to the fluorocar bon ion fluxes as the microwave power is increased or the chamber pres sure is decreased. This relative increase in the F+ ion flux may be ca used by the increased dissociation of the source gas. Changes in the i on flux composition seem to have little effect on the Si and SiO2 etch rates. It was also observed that the F+ ion flux increases as the per centage of hydrogen in a CHF3/H-2 plasma is increased while the neutra l fluorine optical emission intensity decreases for the same condition s. The data suggest that for these conditions dissociative ionization reactions involving fluorine containing molecules make a significant c ontribution to the production of F+, in addition to the ionization of neutral fluorine.