Traditionally process plasmas are often studied and monitored by optical emission spectroscopy. Here, the authors compare experimental measurements from a secondary electron beam excitation and direct process plasma excitation to discuss and illustrate its distinctiveness in the study of process plasmas. They present results that show excitations of etch process effluents in a SF6 discharge and endpoint detection capabilities in dark plasma process conditions. In SF6 discharges, a band around 300 nm, not visible in process emission, is observed and it can serve as a good indicator of etch product emission during polysilicon etches. Based on prior work reported in literature the authors believe this band is due to SiF4 gas phase species.
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Experimental FTIR absorbance measurements were measured as log10(I/I0). We have converted to ln(I/I0) and thus match Eq. (3).