Laser-induced fluorescence detection of as a primary product of Si and reactive ion etching with gas

The radical was detected in the gas phase during the etching of both Si and substrates under reactive ion etching conditions in steady state and in the afterglow of pulsed plasmas, by laser-induced fluorescence (LIF). Spatially and temporally resolved measurements show that there is a major source of these radicals at, or very close to, the etched substrates, and that desorption of as one of the primary products is the most likely explanation. As the absolute concentration was not determined, it is not currently possible to say whether is a major etch product, although the observed signals were large. With an Si substrate, is produced both under steady-state RIE conditions (i.e. in the presence of ion bombardment) and in the afterglow of a pulsed discharge (i.e. by pure chemical etching by F atoms). In contrast, with an substrate, is only produced in the steady-state plasma. The net surface reaction probability of was found to be close to unity on the reactor walls. Some possible gas-phase reactions of are also discussed. The fluorescence lifetime of the excited state of was measured for the first time, giving a value of ns, in good agreement with theoretical estimates.