The use of segmented cathodes to determine the spoke current density distribution in high power impulse magnetron sputtering plasmas

Poolcharuansin, Phitsanu; Estrin, Francis Lockwood; Bradley, James W.

doi:10.1063/1.4918720

Cited by 30 publications

(43 citation statements)

References 37 publications

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“…This proposition is supported by spectroscopic images of ionization zones in HiPIMS, which showed that the highest ion densities are within the ionization zone. 57,61 If the light intensity is approximately proportional to the ion density, then, based on the reasoning of Section IV E, the spatial distribution of the ion density is similar to the spatial distribution of V p À V f as presented in Figs. 10 and 11 and in supplementary materials S6 and S7.…”

Section: Spatial Distribution and Transport Of Ions And Implicatimentioning

confidence: 99%

Plasma potential of a moving ionization zone in DC magnetron sputtering

Panjan

Anders

2017

Journal of Applied Physics

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Using movable emissive and floating probes, we determined the plasma and floating potentials of an ionization zone (spoke) in a direct current magnetron sputtering discharge. Measurements were recorded in a space and time resolved manner, which allowed us to make a three-dimensional representation of the plasma potential. From this information we could derive the related electric field, space charge, and the related spatial distribution of electron heating. The data reveal the existence of strong electric fields parallel and perpendicular to the target surface. The largest E-fields result from a double layer structure at the leading edge of the ionization zone. We suggest that the double layer plays a crucial role in the energization of electrons since electrons can gain several 10 eV of energy when crossing the double layer. We find sustained coupling between the potential structure, electron heating, and excitation and ionization processes as electrons drift over the magnetron target. The brightest region of an ionization zone is present right after the potential jump, where drifting electrons arrive and where most local electron heating occurs. The ionization zone intensity decays as electrons continue to drift in the Ez × B direction, losing energy by inelastic collisions; electrons become energized again as they cross the potential jump. This results in the elongated, arrowhead-like shape of the ionization zone. The ionization zone moves in the –Ez × B direction from which the to-be-heated electrons arrive and into which the heating region expands; the zone motion is dictated by the force of the local electric field on the ions at the leading edge of the ionization zone. We hypothesize that electron heating caused by the potential jump and physical processes associated with the double layer also apply to magnetrons at higher discharge power, including high power impulse magnetron sputtering.

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Section: Spatial Distribution and Transport Of Ions And Implicatimentioning

confidence: 99%

Plasma potential of a moving ionization zone in DC magnetron sputtering

Panjan

Anders

2017

Journal of Applied Physics

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“…The spoke has been well characterized within a number of experimental devices, including Hall thrusters [3,4,5,6,7,8,9,10,11,12,13,14,15], planar magnetrons [16,17,18,19,20,21,22,23], cylindrical magnetrons [24,25] and Penning discharges [26,27,28]. These devices feature cylindrical geometry, with electron drift and spoke propagation occurring in the azimuthal direction.…”

Section: Introductionmentioning

confidence: 99%

Scaling of spoke rotation frequency within a Penning discharge

et al. 2018

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A rotating plasma spoke is shown to develop in two-dimensional full-sized kinetic simulations of a Penning discharge cross-section. Electron cross-field transport within the discharge is highly anomalous and correlates strongly with the spoke phase. Similarity between collisional and collisionless simulations demonstrates that ionization is not necessary for spoke formation. Parameter scans with discharge current I d , applied magnetic field strength B and ion mass m i show that spoke frequency scales with eE r L n /m i , where E r is the radial electric field, L n is the gradient length scale and e is the fundamental charge. This scaling suggests that the spoke may develop as a non-linear phase of the collisionless Simon-Hoh instability.

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“…These zones of intense plasma follow the E × B drift (other drifts in the same direction are included) of the electrons with a velocity of about 1/10 of the electrons' drift velocity and their motion seems to be a consequence of the "evacuation" of ions from their location of production (ionisation) [10]. The number and the shape of the zones depend on the discharge current [11,12]. Typically, the zones reveal an arrow-like shape with the tip pointing in the direction of the motion, but at higher currents it changes to a rather globular appearance which appears to be associated to a change of the ionization zones' plasma and potential distribution in the direction perpendicular to the target, as fast imaging techniques suggest [13].…”

Section: Introductionmentioning

confidence: 99%

Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbO_xfilm growth

Franz

Clavero

Kolbeck

et al. 2016

Plasma Sources Sci. Technol.

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The ion energies and fluxes in the high power impulse magnetron sputtering plasma from a Nb target were analysed angularly resolved along the tangential direction of the racetrack. A reactive oxygen-containing atmosphere was used as such discharge conditions are typically employed for the synthesis of thin films. Asymmetries in the flux distribution of the recorded ions as well as their energies and charge states were noticed when varying the angle between mass-energy analyser and target surface. More positively charged ions with higher count rates in the medium energy range of their distributions were detected in +E × B than in −E × B direction, thus confirming the notion that ionisation zones (also known as spokes or plasma bunches) are associated with moving potential humps. The motion of the recorded negatively charged high-energy oxygen ions was unaffected. NbO x thin films at different angles and positions were synthesised and analysed as to their structure and properties in order to correlate the observed plasma properties to the film growth conditions. The chemical composition and the film thickness varied with changing deposition angle, where the latter, similar to the ion fluxes, was higher in +E × B than in −E × B direction.

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The use of segmented cathodes to determine the spoke current density distribution in high power impulse magnetron sputtering plasmas

Cited by 30 publications

References 37 publications

Plasma potential of a moving ionization zone in DC magnetron sputtering

Plasma potential of a moving ionization zone in DC magnetron sputtering

Scaling of spoke rotation frequency within a Penning discharge

Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbO_xfilm growth

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The use of segmented cathodes to determine the spoke current density distribution in high power impulse magnetron sputtering plasmas

Cited by 30 publications

References 37 publications

Plasma potential of a moving ionization zone in DC magnetron sputtering

Plasma potential of a moving ionization zone in DC magnetron sputtering

Scaling of spoke rotation frequency within a Penning discharge

Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbOxfilm growth

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Influence of ionisation zone motion in high power impulse magnetron sputtering on angular ion flux and NbO_xfilm growth