Spatiotemporal synchronization of drift waves in a magnetron sputtering plasma

Martines, E.; Zuin, M.; Cavazzana, R.; Adámek, Jiřı́; Antoni, V.; Serianni, G.; Spolaore, M.; Vianello, N.

doi:10.1063/1.4898693

Cited by 4 publications

(4 citation statements)

References 19 publications

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“…At powers below 25 W cm −2 (∼1 A at a 2" planar target), during dcMS operation, only one spoke has been observed above the racetrack of the 2" circular target [17,34]. On larger magnetrons, with 10 cm diameter, spokes with mode numbers four and five have been observed [39]. At powers around 25 W cm −2 (∼1 A at a 2" planar target), during HiPIMS operation, the plasma behaviour becomes stochastic with the spoke rotation changing from retrograde E × B to E × B rotation.…”

Section: Spoke Mode Numbermentioning

confidence: 99%

Spokes in high power impulse magnetron sputtering plasmas

Hecimovic

Keudell²

2018

J. Phys. D: Appl. Phys.

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High power impulse magnetron sputtering (HiPIMS) is a deposition technique where a metal magnetron target is sputtered in a high density plasma to synthesize thin layers with superior properties on a substrate material. These plasmas are characterised by short pulses in the range of 50 µs to 200 µs and very high peak powers in the range of several kW/cm 2 per target area. The understanding of these dynamic plasmas is of upmost interest for the further development of this coating technique. Fast camera measurements revealed the formation of localised ionisation zones in these plasmas that propagate with a velocity of the order km/s. In the case of a circular magnetron, the movement of these ionisation zones appears like the movement of a set of spokes, which led to this common expression spoke to illustrate the pattern formation in these high density plasmas. The analysis and understanding of the spoke phenomenon is still a matter of an open debate, because the analysis and the theoretical description is hampered by the inherent complexity of these plasmas. In this paper, we review the experimental observations of the spoke phenomenon and highlight several approaches for their theoretical explanation.

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Section: Spoke Mode Numbermentioning

confidence: 99%

Spokes in high power impulse magnetron sputtering plasmas

Hecimovic

Keudell²

2018

J. Phys. D: Appl. Phys.

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“…With this automated procedure it is possible to do statistical analysis and to derive histograms of spoke patterns for given discharges conditions. However, the method cannot discriminate between low frequency drift-modes (∝10 kHz) in dcMS-like regimes [20] or high frequency spoke-modes (∝100 kHz) [3]. Already small modulations in light intensity will produce peaks in the FFT and yield quasi-mode numbers.…”

Section: Statistical Determination Of Spoke Mode Numbersmentioning

confidence: 99%

Influence of spokes on the ionized metal flux fraction in chromium high power impulse magnetron sputtering

Biskup¹,

Maszl²,

Breilmann³

et al. 2018

J. Phys. D: Appl. Phys.

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High power impulse magnetron sputtering (HiPIMS) discharges are an excellent tool for deposition of thin films with superior properties. By adjusting the plasma parameters, an energetic metal and reactive species growth flux can be controlled. This control requires, however, a quantitative knowledge of the ion-to-neutral ratio in the growth flux and of the ion energy distribution function to optimize the deposited energy per incorporated atom in the film. This quantification is performed by combining two diagnostics, a quartz crystal microbalance (QCM) combined with an ion-repelling grid system (IReGS) to discriminate ions versus neutrals and a HIDEN EQP plasma monitor to measure the ion energy distribution function (IEDF). This approach yields the ionized metal flux fraction (IMFF) as the ionization degree in the growth flux. This is correlated to the plasma performance recorded by time resolved ICCD camera measurements, which allow to identify the formation of pronounced ionization zones, so called spokes, in the HiPIMS plasma. Thereby an automatic technique was developed to identify the spoke mode number. The data indicates two distinct regimes with respect to spoke formation that occur with increasing peak power, a stochastic regime with no spokes at low peak powers followed by a regime with distinct spokes at varying mode numbers at higher peak powers. The IMFF increases with increasing peak power reaching values of almost 80% at very high peak powers. The transition in between the two regimes coincides with a pronounced change in the IMFF. This change indicates that the formation of spokes apparently counteracts the return effect in HiPIMS. Based on the IMFF and the mean energy of the ions, the energy per deposited atom together with the overall energy flux onto the substrate is calculated. This allows us to determine an optimum for the peak power density around 0.5 kW cm−2 for chromium HiPIMS.

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“…Several authors studied the temporal fluctuations in the floating potential and some associated it with the moving ionization zones. 8,[33][34][35][36][37] Such measurements are relatively simple but offer a little insight into the properties of plasma since the motion of charged particles is affected by the gradient of the plasma potential and not by the gradient of the floating potential.…”

Section: Introductionmentioning

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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Spatiotemporal synchronization of drift waves in a magnetron sputtering plasma

Cited by 4 publications

References 19 publications

Spokes in high power impulse magnetron sputtering plasmas

Spokes in high power impulse magnetron sputtering plasmas

Influence of spokes on the ionized metal flux fraction in chromium high power impulse magnetron sputtering

Plasma potential of a moving ionization zone in DC magnetron sputtering

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