A Gas-Discharge Sputtering Device Based on a Planar Magnetron with an Ion Source
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A Gas-Discharge Sputtering Device Based on a Planar Magnetron with an Ion Source A. P. Semenova,*,**, I. A. Semenovaa, D. B.-D. Tsyrenova, and E. O. Nikolaeva a Institute
of Physical Materials Science, Siberian Branch, Russian Academy of Sciences, Ulan-Ude, 670047 Russia *e-mail: [email protected] **e-mail: [email protected] Received March 24, 2020; revised April 4, 2020; accepted April 5, 2020
Abstract—A gas-discharge device based on a planar magnetron and a plasma ion source is considered. The longitudinal injection of an ion beam into the magnetron and sputtering of the cathode and central anode of the magnetron by the ion beam contributes to the ignition of an anomalous low-pressure (below 8 × 10–2 Pa) glow discharge in the magnetron. It has been found that the discharge ignition voltage decreases with an increase in the ion energy and depends on the ion-beam current in a threshold manner. The prospects of expanding the functionality of planar magnetrons in the synthesis of nanostructured TiN–Cu composite coatings are shown. DOI: 10.1134/S0020441220050218
INTRODUCTION An anomalous glow discharge is used in planartype magnetron sputtering systems that are widely used for growing coatings for various functional purposes [1, 2]. The discharge is ignited in crossed electric and magnetic fields, so that the magnetic field confines the discharge plasma near the target cathode, thus contributing to an increase in the plasma density and, as a result, to an increase in the ion current to the cathode. The discharge is characterized [3, 4] first by a constant area on the cathode, which receives current, and, second, by an increase in the discharge current with an increase in the discharge voltage. As a rule, the discharge is stably ignited and stably sustained in a pressure range of the working gas of 0.2–6 Pa [4]. However, at these pressures, the relationship l < λ, where l is the cathode–substrate distance, and λ is the free path of atoms, is not valid, and a collision-free transfer to the substrate of knockedout atoms, which leave the cathode as a result of the cathode sputtering by plasma ions accelerated in the cathode layer, does not occur. The free path of sputtered atoms in a gas at a pressure of 0.2–6 Pa is 10–3– 10–2 m. Under these conditions, the inequality l < λ can hardly be fulfilled with allowance for the uncontrolled radiation and thermal effect of the discharge plasma on the coating and the inability to achieve its uniform thickness. At the same time, the collision-induced transfer of sputtered atoms makes it difficult to obtain coatings with a perfect structure and achieve the required accuracy of reproducing the growth regimes.
The condition l < λ is met at pressures below 0.1 Pa, for which λ > 10–1 m. However, at low pressures, the ignition voltage strongly depends on the pressure [4] and the discharge is initiated at relatively high voltages that exceed 10 kV. Therefore, at low pressures a situation often occurs where the discharge ignition voltage exceeds the disc
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