Time resolved 2-D optical imaging of a pulsed unbalanced magnetron plasma

Bradley, James W.; Clarke, Gregory; Braithwaite, Nicholas; Bryant, Paul M.; Kelly, Peter

doi:10.1088/0963-0252/15/2/s06

Cited by 13 publications

(9 citation statements)

References 35 publications

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“…The maxima are strongly dependent on the position in the discharge. The first one is predominantly developed in the bulk, the second is especially pronounced in the region with a high magnetic field parallel to the target surface, which is in good agreement with optical emission results found for a similar magnetron 19. The different locations of increased plasma density are mostly due to the different initial position of the electrons causing the ionisation maxima and the fact that electrons leading to the first maximum do not acquire the energy equivalent to the full discharge voltage but those responsible for the second maximum do.…”

Section: Resultssupporting

confidence: 90%

“…To understand these phenomena better, space‐ and time‐resolved measurements of the discharge development are necessary. First two‐dimensional studies of the discharge by OES have been reported recently,19 also a cross‐sectional study perpendicular to the target 20. Further investigations have been done by emissive probes to spatio‐temporally determine the plasma potential 21,22.…”

Section: Introductionmentioning

confidence: 99%

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Two-Dimensional Double Probe Study of the Temporal Evolution of the Charge Carrier Density in a Pulsed Magnetron

Welzel

Dunger

Richter

2007

Plasma Process. Polym.

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An asymmetric‐bipolar pulsed magnetron discharge was spatially studied in two dimensions with a time‐resolved Langmuir double probe. The cylindrical magnetron was equipped with an Mg target. The development of the charge carrier density during one pulse reveals the same characteristic as the two‐peak structure at the beginning of the ‘on’ phase which we have observed earlier. This temporal peak structure changes with position within the volume of the discharge between target and substrate. While the first maximum is dominant in the discharge centre with the plasma torus of the magnetron only weakly pronounced, the second peak is very intense in the torus region and comparably weak in the whole rest of the discharge. This peak distribution is explained by a simple model based on the acceleration of electrons left over from the previous pulse.

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Section: Resultssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Two-Dimensional Double Probe Study of the Temporal Evolution of the Charge Carrier Density in a Pulsed Magnetron

Welzel

Dunger

Richter

2007

Plasma Process. Polym.

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“…The latter phenomena would indicate there is a short-lived burst (∼µs duration) of electron current to the walls. These electrons may be a remnant of the sheathaccelerated 'fast' electrons emanating from the target and may be responsible for flashes in the Ar(I) optical output [29] at this time in cycle.…”

Section: Resultsmentioning

confidence: 99%

The current-density distribution in a pulsed dc magnetron deposition discharge

Vetushka

Bradley

2007

J. Phys. D: Appl. Phys.

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Using a carefully constructed magnetic probe (a B-dot probe) the spatial and temporal evolution of the perturbation in the magnetic field ΔB in an unbalanced pulsed dc magnetron has been determined. The plasma was run in argon at a pressure of 0.74 Pa and the plasma ions sputtered a pure graphite target. The pulse frequency and duty were set at 100 kHz and 55%, respectively. From the ΔB measurements (measured with magnitudes up to about 0.01 mT) the axial, azimuthal and radial components of the total current density j in the plasma bulk were determined. In the plasma ‘on’ phase, the axial current density jz has a maximum value of approximately 200 A m−2 above the racetrack region, while high values in the azimuthal current density jΦ are distributed in a region from 1 to 3 cm into the bulk plasma with jΦ exceeding 350 A m−2.In the ‘off’ phase of the plasma, jz decays almost instantaneously (at least within the 100 ns time-resolution of the ΔB measurements) as the electric field collapses; however, jΦ decays with a characteristic time constant of about 1 µs. This slow decay can be attributed to the presence of decaying Grad-B and curvature drifts, with their rates controlled by the decay in the plasma density. A comparison between axial and azimuthal current densities in the plasma ‘on’ time, when the plasma is being driven, strongly indicates that classical transport does not operate in the magnetron discharge.

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“…The generation of fast electrons at the voltage transitions was also observed using wavelength filtered 2D optical imaging of the whole plasma. These filters were selected to transmit specific lines in Ar I and Ti I as reported in [35].…”

Section: Energetic Spikes In T Ementioning

confidence: 99%

Physics and phenomena in pulsed magnetrons: an overview

Bradley¹,

Welzel²

2009

J. Phys. D: Appl. Phys.

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This paper reviews the contribution made to the observation and understanding of the basic physical processes occurring in an important type of magnetized low-pressure plasma discharge, the pulsed magnetron.In industry, these plasma sources are operated typically in reactive mode where a cathode is sputtered in the presence of both chemically reactive and noble gases typically with the power modulated in the mid-frequency (5–350 kHz) range. In this review, we concentrate mostly, however, on physics-based studies carried out on magnetron systems operated in argon. This simplifies the physical–chemical processes occurring and makes interpretation of the observations somewhat easier.Since their first recorded use in 1993 there have been more than 300 peer-reviewed paper publications concerned with pulsed magnetrons, dealing wholly or in part with fundamental observations and basic studies. The fundamentals of these plasmas and the relationship between the plasma parameters and thin film quality regularly have whole sessions at international conferences devoted to them; however, since many different types of magnetron geometries have been used worldwide with different operating parameters the important results are often difficult to tease out. For example, we find the detailed observations of the plasma parameter (particle density and temperature) evolution from experiment to experiment are at best difficult to compare and at worst contradictory.We review in turn five major areas of studies which are addressed in the literature and try to draw out the major results. These areas are: fast electron generation, bulk plasma heating, short and long-term plasma parameter rise and decay rates, plasma potential modulation and transient phenomena. The influence of these phenomena on the ion energy and ion energy flux at the substrate is discussed. This review, although not exhaustive, will serve as a useful guide for more in-depth investigations using the referenced literature and also hopefully as an inspiration for future studies.

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Time resolved 2-D optical imaging of a pulsed unbalanced magnetron plasma

Cited by 13 publications

References 35 publications

Two-Dimensional Double Probe Study of the Temporal Evolution of the Charge Carrier Density in a Pulsed Magnetron

Two-Dimensional Double Probe Study of the Temporal Evolution of the Charge Carrier Density in a Pulsed Magnetron

The current-density distribution in a pulsed dc magnetron deposition discharge

Physics and phenomena in pulsed magnetrons: an overview

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