Characterization of a microwave plasma jet containing Ar-CH4 gas mixture

Cinelli

J. Phys. D: Appl. Phys.

et al. 1999

Microwave expansion of a plasma is certainly a promising process by which to obtain a large-diameter plasma profile; however, it generates instability regions and local inhomogeneities. The purpose of this work is to study the wave-propagation conditions and plasma-expansion profile in a pure argon discharge and in argon-methane mixture. Spatially resolved plasma parameters are measured using an array of electrostatic probes (simple and double) moving along the discharge axis. This device gives radial and axial measurements which are correlated to the spatially resolved Ar(420 nm) emission line intensity. We show that, as expected, the wave-propagation conditions are satisfied within the luminous part of the discharge. In this region the electron energy distribution function (EEDF) can be roughly approximated by using a Maxwell distribution function of low temperature (about 1000 K). The absorbed microwave power is mainly transferred to electrons as potential energy. Instabilities appear at the edge of this luminous region, where the wave-propagation conditions are not satisfied. In this region the EEDF is strongly disturbed and cannot be approximated using a Maxwell distribution function. The microwave incident power is mainly reflected, so the potential energy of electrons decreases strongly. Nevertheless, the kinetic energy of electrons increases because of stochastic electron heating due to strong inhomogeneities in the charged particle density producing local electrical fields. When methane is mixed with argon, the energy necessary to maintain an electron free in the plasma increases with increasing frequency of inelastic collisions. Consequently, the plasma expansion length decreases with increasing percentage of methane added to argon.

Section: In Pure Argonmentioning

confidence: 74%

A spatially resolved plasma diagnostic in an expanding microwave discharge containing an Ar- gas mixture: uniformity and stability of the discharge

Cinelli

J. Phys. D: Appl. Phys.

et al. 1999

“…We observe an increase of the electron density and a decrease of the electron energy simultaneously to the plasma expansion. Moreover, we have shown 17 that according to the experimental conditions, the radial distribution of the Ar(420 nm) emission line intensity observed by optical emission spectroscopy (after Abel inversion) is maximum on the side of the plasma expansion and minimum at the center. Such results have also been observed by Moisan et al 18 in surface-wave excited discharge.…”

Section: Figmentioning

confidence: 84%

Dielectric properties in microwave remote plasma sustained in argon: Expanding plasma conditions

2012

Physics of Plasmas

Self Cite

This work is devoted to the study of the relative permittivity in argon expanding plasma produced below a microwave discharge sustained in a quartz tube and working at 2.45 GHz. We discuss results and explain the microwave propagation within the reactor, outside the quartz tube. It is shown that at low pressures (133 Pa) and at powers ranging from 100 W to 400 W, the wave frequency remains lower than the plasma frequency anywhere in the expanding plasma. Under these conditions, the real part of the relative permittivity is negative and the wave is reflected. Surprisingly, in these conditions, the plasma is produced inside and outside the quartz tube, below the wave launcher. This effect can be explained considering a surface wave propagating at the surface of the quartz tube then into the reactor, on the external surface of the expanding plasma below the quartz tube. V

“…In contrast to this result, only very slight amounts of nitrogen and oxygen are transferred into the films located at 15.5 cm from the discharge center, the concentration values are quite within the range of the detection limit of the method (Figure 6(b)). This result is correlated to the geometry of pure N 2 plasma which remains in a confined space around the center of the discharge: the density of electrons of 0.16 × 10 16 m -3 in pure N 2 plasma is lower than the one corresponding to pure Ar plasma which ranges from 0.5 to 1 × 10 16 m -3 [20]. So, the substrate located at 15.5 cm from the center of the discharge is probably exposed to the postdischarge where the amount of active species is low.…”

Section: Molybdenum Films Exposed To Pure N 2 Plasmamentioning

confidence: 94%

“…However, in reality, the plasma is expanded outside the quartz tube in the stainless steel part where the value of the permittivity is unknown. Moreover, according to previous works conducted on Ar gas with emission spectroscopy, the intensity of emission lines of some species increases on the edge of plasma [20]. The electromagnetic wave seems to propagate on the surface of plasma, drawing a bright cone inside the stainless steel part of the reactor.…”

Section: Conditions Of Formation Of An Expanding Plasmamentioning

confidence: 99%

A Thermochemical Process Using Expanding Plasma for Nitriding Thin Molybdenum Films at Low Temperature

Jauberteau¹,

Jauberteau²,

Touimi³

et al. 2012

ENG

The mechanical and chemical properties of transition metal nitrides are very attractive for numerous industrial applications. Thin nitride films are expected to be good diffusion barrier in microelectronic devices. Nitrogen diffuses into the whole thickness of the molybdenum film heated at low temperature and exposed to expanding plasma of (Ar-N 2 -H 2 ) compared with pure N 2 plasma. NH x species in the plasma are produced by different homogeneous or heterogeneous reactive mechanisms that results in an expansion of the plasma compared with pure N 2 plasma. NH x species and probably H atoms improve the transfer of nitrogen into the metal by preventing the formation of MoO 2 oxides which act as a barrier of diffusion for nitrogen.