Titration Method for Measuring Fluorine Atom Concentration in Microwave Plasma Etching

Abstract
A titration method has seen developed to measure the concentration of fluorine (F) atom in microwave plasma etching. A rapid reaction of F atoms with H2 gas is used as a titration reaction to determine the absolute F atom concentration. Applying the present method to SF6 microwave discharge, the F atom concentration is measured under various discharge conditions. The F atom concentration is 2.9-4.0×1011 cm-3 at a typical operating pressure of 6.7×10-2 Pa and a microwave power of 200 W. It is confirmed that relative changes in the concentration agree well with those obtained with the optical spectroscopic method.

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