Electron density measurements on an inductively coupled plasma with a one-port microwave interferometer

Abstract

A one-port microwave interferometer has been employed to measure the electron density in a conventional reactor for plasma-enhanced chemical vapour deposition (PECVD). As opposed to standard two-port configurations, which require two accessible viewports in the reactor, this setup uses only one port and is therefore readily coupled to standard industrial vacuum equipment. The interferometer works at 45.75 GHz and separates forwarded and reflected waves. A microwave mirror is positioned at the reactor wall opposite the viewing port. The capability of the method is demonstrated on the basis of exemplary measurements in an inductively coupled plasma (ICP, 13.56 MHz) suitable for PECVD. Line-integrated electron densities are measured for different conditions (Ar, p = 0.1-1 Pa, P rf = 30-1000 W). Langmuir probe measurements provide radial profiles of the electron density and are used as a comparative reference. These profiles are fitted with Bessel functions and serve as the basis for the interpretation of the interferometric data in terms of peak density, where the amplitude of these generic profiles is used as the free parameter. The densities obtained are in good agreement with the Langmuir probe results. Maximum values 1 × 10 18 m −3 are obtained in the centre of the vessel at an axial distance of 0.24 m from the antenna window of the ICP source.

Characterization of inductively coupled plasma generated by a quadruple antenna

“…The microwave interferometry method allows one to measure the electron density in the plasma by measuring the phase shift of microwaves transmitted through the plasma [27]. For example, Andrasch et al [28] used a microwave interferometer to determine the electron density of ICP generated in a cylindrical volume in Ar gas at a pressure range 0.1-10 Pa. For calculating density, the radial density profile, which was determined using a Langmuir probe, was used.…”

Inactivation of Vegetative Microorganisms and Bacillus atrophaeus Endospores by Reactive Nitrogen Species (RNS)

“…The coefficient of diffusion can be mentioned with 0.2062 cm 2 · s −1 for at 26 °C (0.3279 cm 2 · s −1 for at 117 °C) and 0.1572 cm 2 · s −1 for (0.2547 cm 2 · s −1 for ) . A higher diffusion coefficient leads to faster transport of chemical species . The higher diffusion coefficient of possibly leads to the small decrease seen in the first 5 min, afterwards the obtained plateau may be a result from the alteration of the metastabil to the stabile .…”

“…[39,40] A higher diffusion coefficient leads to faster transport of chemical species. [41] The higher diffusion coefficient of NO possibly leads to the small decrease seen in the first 5 min, afterwards the obtained plateau may be a result from the alteration of the metastabil NO to the stabile NO 2 (2).…”

Electron density in amplitude modulated microwave atmospheric plasma jet as determined from microwave interferometry and emission spectroscopy

“…to objects with dimensions comparable to the wavelength. Recent research employs all sorts of advanced approaches, including heterodyne detection [33][34][35][36], dual lasers [37], holographic interferometer [38], transmission line design [39], one-port microwave interferometer [36,40], combined techniques [41], radio frequencies [42], harmonics [43], dielectric waveguides [44][45][46], and micro-strip line [47].…”