Optical emission spectroscopy of pulsed hexalfuoropropylene oxide and tetrafluoroethylene plasmas

Abstract

The optical emission spectra of tetrafluoroethylene (TFE) and hexafluoropropylene oxide (HFPO) have been examined for chemistry and electron distribution transients as a function of plasma pulsing, under depositing conditions (1 torr). The major identifiable peaks in these plasmas are attributable to CF2 and CF. Other expected species, including CF3, atomic F and atomic C are not observed. HFPO plasmas show significant emission from CO and O. Comparison of CF2 emission transients to absolute absorption measurements show that the continuum emission surrounding CF2 is not attributable to CF2+ emission, as has been previously proposed, but is likely rovibrational overlap. Argon emission in TFE shows a relatively slow transient toward steady state (∼20 ms), implying slower chemistry transients, such as attachment, control the electron transient in pulsed TFE plasmas. In HFPO plasmas, CO and O actinometry are applied. CO emission trends suggest that CO is actually produced during the plasma off times, and is here attributed to etching reactions in the film. The rotational structure of CO is also examined and fit to estimate plasma rotational temperature, giving temperature transients on the order of ∼20 ms.