Space–time resolved kinetics of mixed rare-gas-attaching gas plasmas

Abstract

Because plasma processing recipes are usually determined empirically, it is desirable to develop methods for isolating kinetic mechanisms in discharges through gas mixtures. In this manuscript, we show how space–time resolved measurements of plasma-induced emission and laser-induced fluorescence intensities are used to distinguish between electronic, ionic, and neutral mechanisms for excited-state production in radio frequency discharges containing Ar and BCl3. Although it was expected that the Ar metastable state would affect the degree of BCl3 dissociation, the mechanism uncovered using in situ diagnostics had not been considered previously: superelastic collisions between Ar metastables and electrons produce hot electrons capable of dissociating BCl3 more efficiently. By contrast, direct dissociative energy transfer from Ar metastables to BCl3 is unimportant. This mechanism leads to a narrow concentration range over which the dissociative excitation of BCl3 is increased tenfold relative to the pure BCl3 discharge.