THE ETCHING OF CHF3 PLASMA POLYMER IN FLUORINE-CONTAINING DISCHARGES

The etching of CHF3 plasma polymer in fluorine containing electrical discharges was studied. The fluorine sources were SF6, CF4, and mixtures of the two. For discharges in SF6 and mixtures of SF6 and CF4, a good correlation was obtained between the etch rate and the atomic fluorine concentration measured using actinometry. For CF4, the etch rate was found to be much higher than that predicted from this correlation. This is attributed to the energetic ion bombardment of the polymer surface in the CF4 discharge. X-ray photoelectron spectroscopy analysis of the etched polymer surface shows an increased fluorine content, but the F:C ratio was independent of the etching conditions. The implications of the results for the kinetics of fluorocarbon plasma polymerization are discussed.