Abstract
A novel optical emission spectroscopy (OES) technique for the determination of electron temperatures and densities in low-pressure argon discharges is compared with Thomson scattering (TS). The emission spectroscopy technique is based on the measurement of certain line ratios in argon and a collisional–radiative model (CRM) including metastable transport. The investigations are carried out in a planar inductively coupled neutral loop discharge (NLD) over a wide range of pressures, p = 0.05 Pa–5 Pa. This discharge is a weakly magnetized novel radio-frequency (rf) plasma source, proposed for plasma etching. The NLD is operated in pure argon at a frequency of f = 13.56 MHz and powers varied between P = 1 kW and 2 kW. Both diagnostics, OES and TS, are applied in parallel. The electron energy distribution functions obtained by TS are clearly Maxwellian at low pressures but exhibit a certain enhancement of the energetic tail at higher pressures. Electron densities and temperatures obtained by both diagnostic techniques are compared. Further, absolute numbers of the metastable densities derived from the measurement by the CRM are compared with earlier measurements under similar conditions. Excellent agreement is found throughout if depletion of the neutral gas density by increasing gas temperature and electron pressure is included in the CRM. Electron pressure is the dominant depletion mechanism at gas pressures p ⩽ 0.1 Pa and rf powers P > 1 kW. There, the electron pressure exceeds more than 3 times the neutral pressure and the ionization degree approaches 7% while at pressures p > 1 Pa the degree of ionization is relatively low (<10−3) and neutral gas depletion is dominated by gas heating.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.