Spectroscopic imaging of self-organization in high power impulse magnetron sputtering plasmas

Andersson, Joakim; Ni, P.; Anders, André

doi:10.1063/1.4817257

Cited by 56 publications

(64 citation statements)

References 18 publications

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“…3). This suggests that spectrally integrated [2][3][4]11 and spectrally selected 19 images show not just regions of enhanced excitation and ionization but regions of elevated electric potential. Images of ionization zones can and should be interpreted as distributions of electric potential and related electron energy.…”

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confidence: 99%

“…26 Our observations also indicated a disappearance or "smoothing" of ionization zones at high pressure, or more precisely, at high neutral atom density, which can be achieved even in the pure self-sputtering mode in vacuum. 27 Spectroscopic imaging of ionization zones 19 revealed that the higher the excitation level, the sharper and more spatially limited the visible emission are, which can be interpreted as the shape of the potential hump (Fig. 3).…”

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confidence: 99%

“…spokes 11,16,17 ), and associated potential humps. 18 Fast imaging of HiPIMS [2][3][4]11,19 and direct current magnetron sputtering 20 (dcMS) plasmas indicated that ionization rate and emission of light and particles are usually not uniformly distributed but concentrated in bright zones that move along the racetrack. Additionally, measurements of charged particle fluxes have revealed important features: (a) ion and electron fluxes appear in short pulses (jets), 21 (b) doubly charged ions have approximately twice the energy of singly charged ions, 18,21 and (c) ions emitted in the E× B direction have several 10 eV higher energy than ions going in the opposite direction, i.e., leaving the magnetron in the −E× B direction.…”

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Localized heating of electrons in ionization zones: Going beyond the Penning-Thornton paradigm in magnetron sputtering

Anders

2014

Applied Physics Letters

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The fundamental question of how energy is supplied to a magnetron discharge is commonly answered by the Penning-Thornton paradigm invoking secondary electrons. Recently, Huo and coworkers (Plasma Sources Sci. Technol. 22, 045005 (2013)) used a global discharge model to show that electron heating in the electric field of the magnetic presheath is dominant over heating by secondary electrons. In this contribution, this concept is applied locally taking into account the electric potential structure of ionization zones. Images of ionization zones can and should be interpreted as diagrams of the localization of high electric potential and related electron energy.

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Localized heating of electrons in ionization zones: Going beyond the Penning-Thornton paradigm in magnetron sputtering

Anders

2014

Applied Physics Letters

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“…Sputtering was done in pure argon with a flow rate of 60 sccm resulting in a pressure of 0.5 Pa. The choice of aluminum allows us to do a direct comparison with images obtained in a recent study of HiPIMS discharges [10]. In fact, the target and magnetron were the same, and the power supply (SIPP by Melec) was simply switched to dc operation.…”

Section: Introductionmentioning

confidence: 99%

Drifting Ionization Zone in DC Magnetron Sputtering Discharges at Very Low Currents

Anders

Andersson

2014

IEEE Trans. Plasma Sci.

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Fig. 1. False-color fast camera images of aluminum sputtered in 0.5 Pa of argon. The top 8 images show the blurring of a drifting ionization zone when the image exposure time exceeds 5 μs (the discharge current was 30 mA). The center 4 side-view images were taken with an exposure time of 500 ns for different discharge currents; z is the distance from the target surface. The lower 4 images, also taken with 500 ns exposure time, illustrate the existence of one zone at different currents. Note that the camera was always in the linear regime; the image intensifier's gain had to be increased to make plasma visible at short exposures, and decreased to avoid saturation at long exposures, and hence the apparent brightness should be judged with caution.

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“…The generation mechanism of the spokes and their influence on the transport properties are not fully understood yet. Based on these spokes, energetic ions that have been observed in lateral directions to the magnetron target by Lundin et al [21] who explained these energetic species by a generation mechanism based on a two stream instability interacting with the spoke region; v) Anders and Andersson et al [24,25] proposed a model which incorporates a double layer (DL) when the HiPIMS plasma is in the spokes regime. With a DL present the deconfinement and the acceleration of particles to high energies can be explained.…”

Section: Introductionmentioning

confidence: 99%

Origin of the energetic ions at the substrate generated during high power pulsed magnetron sputtering of titanium

Maszl

Breilmann

Benedikt

et al. 2014

J. Phys. D: Appl. Phys.

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Abstract. High power impulse magnetron sputtering (HiPIMS) plasmas generate energetic metal ions at the substrate as a major difference to conventional direct current magnetron sputtering (dcMS). The origin of these very energetic ions in HiPIMS is still an open issue, which is unraveled by using two fast diagnostics: time resolved mass spectrometry with a temporal resolution of 2 µs and phase resolved optical emission spectroscopy with a temporal resolution of 1 µs. A power scan from dcMS-like to HiPIMS plasmas was performed, with a 2-inch magnetron and a titanium target as sputter source and argon as working gas. Clear differences in the transport as well in the energetic properties of Ar + , Ar 2+ , Ti + and Ti 2+ were observed. For discharges with highest peak power densities a high energetic group of Ti + and Ti 2+ could be identified with energies of approximately 25 eV and of 50 eV, respectively. A cold group of ions is always present. It is found that hot ions are observed only, when the plasma enters the spokes regime, which can be monitored by oscillations in the IV-characteristics in the MHz range that are picked up by the used VI-probes. These oscillations are correlated with the spokes phenomenon and are explained as an amplification of the Hall current inside the spokes as hot ionization zones. To explain the presence of energetic ions, we propose a double layer (DL) confining the hot plasma inside a spoke: if an atom becomes ionized inside the spokes region it is accelerated because of the DL to higher energies whereas its energy remains unchanged if it is ionized outside. In applying this DL model to our measurements the observed phenomena as well as several measurements from other groups can be explained. Only if spokes and a double layer are present the confined particles can gain enough energy to leave the magnetic trap. We conclude from our findings that the spoke phenomenon represents the essence of HiPIMS plasmas, explaining their good performance for material synthesis applications. ‡

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Spectroscopic imaging of self-organization in high power impulse magnetron sputtering plasmas

Cited by 56 publications

References 18 publications

Localized heating of electrons in ionization zones: Going beyond the Penning-Thornton paradigm in magnetron sputtering

Localized heating of electrons in ionization zones: Going beyond the Penning-Thornton paradigm in magnetron sputtering

Drifting Ionization Zone in DC Magnetron Sputtering Discharges at Very Low Currents

Origin of the energetic ions at the substrate generated during high power pulsed magnetron sputtering of titanium

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