Measurements of dioxygen fluoride (O2F) in an atmospheric pressure plasma jet

Abstract

When etching tantalum with a coaxial-cylinder-type atmospheric pressure plasma jet (APPJ) in a He∕CF4∕O2 gas mixture, we found that the etch rates vary little with the distance between the plasma region and the substrate. Etch rates decrease by less than a factor of 3 when the distance increases from 0.3to20.3cm in a closed tube that carries the APPJ effluent. These results indicate that reactive species may last up to 40ms in the effluent. Ultraviolet absorption spectroscopy was employed to measure possible reactive species, specifically dioxygen fluoride (O2F) and ozone (O3), in a parallel-plate type APPJ. O2F was found to be a significantly long-lived species, lasting up to 10ms in the effluent with a constant density of about 1015cm−3. Using a measured O3 density profile, the concentration of atomic fluorine (F) was estimated to be about 1013cm−3, which is two orders of magnitude lower than that of O2F at a distance of 1cm away from the APPJ exit. In summary, F atoms produced inside the APPJ combine with O2 molecules, producing O2F molecules, which can live long enough to reach and possibly etch metal surfaces.

Spectroscopy techniques and the measurement of molecular radical densities in atmospheric pressure plasmas

“…220 nm and 300 nm in the Hartley band [134][135][136][137] with a maximum cross-section of ~10 -17 cm 2 . This has made ozone measurements accessible using mercury or D2 lamp sources [138][139][140][141][142] , and thus it has been extensively studied. One potential drawback of probing ozone at this wavelength is the non-specificity resulting from the featureless absorption and therefore the possibility that other species that also absorb at this wavelength will cause erroneous results.…”

Review on VUV to MIR absorption spectroscopy of atmospheric pressure plasma jets

“…[164,165]). In [166], not only ozone but also O 2 F was diagnosed in a parallel plate jet (APPJ) used for etching tantalum with CF 4 admixtures. Most easily, Hg lamps are used because of the dominant emission line at 254 nm at the central absorption wavelength of the Hartley bands.…”

Recent Advances in the Research on Non‐Equilibrium Atmospheric Pressure Plasma Jets

“…The uniform discharge in the APPJ was identified as the α ‐mode of an RF‐discharge 33–35. Since the introduction of the APPJ, quite a few investigations have been reported 34–70. In the following sections, the results of these studies will be summarized.…”

“…Kapton and polyimide have been successfully etched 37, 47. The etching of a variety of non‐organic materials has been demonstrated as well 37, 48, 49, 69. However, in this case, carbon tetrafluoride (CF 4 ) was admixed to an oxygen containing rare gas, which makes the exhaust gas harmful.…”