Cavity-hollow cathode-sputtering source for titanium films

We present results from two mutually independent measurements of plasma and neutral gas flow velocities in a plasma jet deposition system. Operation of a hollow-cathode discharge within the plasma jet nozzle in the pulse regime enables the simple use of a classical Langmuir probe for the plasma flow velocity measurement. In this method, we assume that the plasma is generated solely inside the nozzle during the power impulse and we measure the time of flight of the ions along a known distance between the nozzle end and the probe. The plasma velocity at the plasma jet axis is then determined by differentiation of the dependence of the distance covered by ions on time. As the second method the well-known Pitot tube is used for measurement of the neutral gas velocity. By comparison of both methods we have experimentally proved that the neutral gas flow velocity is almost unaffected by the presence of the plasma, i.e. it does not substantially depend on whether the discharge is switched on or off. The results of both methods correspond well; detected differences are qualitatively explained. It is documented that the plasma jet can be operated both in a subsonic and in a supersonic regime. We present the dependences of the plasma and neutral gas flow velocity on the distance from the cathode, on the pressure in the reactor chamber, and on the flow rate of the working gas.

Section: Introductionmentioning

confidence: 99%

Measurement of the plasma and neutral gas flow velocities in a low-pressure hollow-cathode plasma jet sputtering system

Klusoň¹,

Kudrna²,

Tichý³

2012

“…Deposition applications of thin films in a HC discharge configuration are well established and have been used by several research groups [18,19]. In this section, the possible use of the transparent double grid cathode discharge with axisymmetrically aligned orifices is investigated for sputtering and deposition applications.…”

Section: Technical Applicationsmentioning

confidence: 99%

“…HC-like designs are important in the construction of ion and Hall thrusters [8][9][10][11] and have been studied in recent years for geometry to power scaling [12][13][14]. As deposition sources they present a significant advantage to other well-established sputtering systems such as the magnetron [15,16], allowing also for sputtering of ferromagnetic materials [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Concentric double hollow grid cathode discharges. Spectral investigations and phenomenological approach

Konrad-Soare

Enescu

Dimitriu

et al. 2021

A discharge plasma is created by simultaneously biasing two concentric spherical grids with axisymmetric orifices. In this geometry, space charge structures in the form of multiple quasi-spherical luminous plasma bodies appear simultaneously inside and around the cathodes. The plasma formations are highly interdependent supplying each other with the particle flow and current closure necessary for the maintenance of the discharge. To diagnose these structures, space-resolved cold Langmuir probe measurements and optical emission spectroscopy investigations were performed in the axial direction allowing for the mapping of the axial profiles of plasma potential, electron temperature and density, ion density and optical emission. The existence of an accelerating double layer in the vicinity of the holes has been confirmed here, and in previous research (Teodorescu-Soare C T et al 2016 Phys. Scr. 91 034002; Schrittwieser R W et al 2017 Phys. Scr. 92 044001; Teodorescu-Soare C T et al 2019 Int. J. Mass Spectrom. 436 83). Besides the assessment of the relationship between discharge conditions and plasma parameters in the novel cathode system, the importance of a multiple concentric cathode discharge configuration is revealed for deposition applications.

“…Other hollow cathode style discharges have been used for plasma-enhanced chemical vapor deposition (PECVD) of photovolatics [3][4][5] as well as for a wide range of surface treatments [6,7] or material depositions [8][9][10][11][12][13] outside the PV industry. Hollow cathode style plasma reactors are unique in that they do not require magnetic fields for operation but instead rely on strong electrostatic fields to trap electrons and enhance plasma production.…”

Section: Introductionmentioning

confidence: 99%

Characterization of a hollow cathode styled plasma reactor for photovoltaic applications

Metz¹,

Mahoney²,

Riedel³

et al. 2014

Heated pocket deposition sources are often used for the rapid manufacture of thin film CdS/CdTe photovoltaic devices, however, new process methods are needed to further improve the quality of the films, increase cell efficiency, and reduce production costs. A plasma-enhanced, close-spacing sublimation (PECSS) technique utilizing a hollow cathode style discharge in a heated pocket has recently been developed as a candidate process method. It has been successfully used to eliminate pin holes, to dope CdS with oxygen, and dope CdTe absorption layers; all of which have resulted in higher device efficiencies. This work presents a characterization of plasma properties inside the hollow cathode style reactor including: plasma density, electron temperature, and plasma potential. Additionally, the uniformity of the ion current flux to the substrate is presented for nitrogen/oxygen and argon feed gases by means of in situ surface probes fabricated by segmenting a transparent conductive oxide film on a glass substrate. A three-dimensional model was developed and used to calculate plasma production and transport processes, and to gain an understanding of the relative roles of energetic primaries and bulk cold electrons on spatial ionization rates that develop within the reactor plasma as a function of gas pressure and geometry. Comparisons between the model and experimental measurements are presented and good agreement has been observed when the appropriate spatially varying ionization rates are estimated.