Abstract
Energy Resolved Actinometry is applied to simultaneously measure the radially resolved oxygen dissociation degree and local mean electron energy in a low-pressure capacitively coupled radio-frequency oxygen plasma with an argon tracer gas admixture. For this purpose, the excitation dynamics of three excited states, namely, Ar(2p1), O(3p3P), and O(3p5P), were determined from their optical emission at 750.46 nm, 777.4 nm, and 844.6 nm using Phase Resolved Optical Emission Spectroscopy (PROES). Both copper and silicon dioxide surfaces are studied with respect to their influence on the oxygen dissociation degree, local mean electron energy, and the radial distributions of both quantities and the variation of the two quantities with discharge pressure and driving voltage are detailed. The differences in the measured dissociation degree between different materials are related back to atomic oxygen surface recombination probabilities.
Highlights
Oxygen plasmas have been widely applied in industry for a variety of different surface modifications such as photoresist removal, chemical vapour deposition, and oxidation.1–5 To realize a process where these modifications are reproducible and uniform over a large area, plasma control techniques capable of tailoring the properties of the plasma, including the mean electron energy and reactive species densities, are crucial.6–11 Of particular importance in this context are the radial distributions of both quantities
The excitation dynamics of three excited states, namely, Ar(2p1), O(3p3P), and O(3p5P), were determined from their optical emission at 750.46 nm, 777.4 nm, and 844.6 nm using Phase Resolved Optical Emission Spectroscopy (PROES). Both copper and silicon dioxide surfaces are studied with respect to their influence on the oxygen dissociation degree, local mean electron energy, and the radial distributions of both quantities and the variation of the two quantities with discharge pressure and driving voltage are detailed
twophoton absorption laser-induced fluorescence (TALIF) and VUV absorption are well known for their accuracy, both are challenging to implement in industrial plasma reactors, if spatially resolved measurements are required
Summary
Oxygen plasmas have been widely applied in industry for a variety of different surface modifications such as photoresist removal, chemical vapour deposition, and oxidation. To realize a process where these modifications are reproducible and uniform over a large area, plasma control techniques capable of tailoring the properties of the plasma, including the mean electron energy and reactive species densities, are crucial. Of particular importance in this context are the radial distributions of both quantities. The importance of the choice of excitation cross sections for oxygen atom actinometry has been discussed in detail by Pagnon et al. and it is clear that different combinations of cross sections can lead to the derivation of differing dissociation degrees and/or mean electron energies The value of such an uncertainty is difficult to quantify; it is likely to be systematic and the same for different experimental conditions and as a result still allows for accurate representation of experimental trends. The implications of the observed trends for plasma processing applications are discussed
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