High-Current Magnetron Sputtering System with Arc Blowout

A.A.Bizyukov, A.Y.Kashaba, E.V.Romaschenko*, K.N.Sereda, I.K.Tarasov** and
V.V.Sleptsov***
Kharkiv National University, Department of plasma physics, 31 Kurchatov Ave., Kharkiv, 61108, Ukraine
* East-Ukrainian National University, 1 Vatutin Str., Lugansk, Ukraine
** National Scientific Center “Kharkiv Institute of Physics and Technologies” (NSC KIPT), 1 Academicheskaya Str.,
Kharkiv, 61108, Ukraine
*** “MATI”-RSTU by K.E.Tsiolkovsky, 27, Petrovka str., Moscow 103767, Russia
Abstract. High-current magnetron sputtering system (HCMSS) with arc blowout and suppression of charged particle
fluxes onto a substrate was developed and tested. The magnetic isolation of an anode along with increasing length of
current channel prevent from formation of cathode spots on the sputtered target surface. Operation of the HCMSS in
quasi-pulse mode shows the absence of visible cathode spots on the cathode surface and arc current channels between the
cathode and anode. High discharge voltage (400 V) along with high currents (40-80 A) indicate that the HCMSS operates
in a magnetron mode, i.e. transition of the discharge into the arc mode at the given discharge parameters is successfully
suppressed.
Keywords: magnetron sputtering system, arc blowout.
PACS: 52.77.–j, 52.50.Dg, 52.75.–d
INTRODUCTION
Last time pulse working regimes of magnetron sputtering system (MSS) are intensively investigating and
equipment for new technological problems solving are developing [1]. It is conditioned on a number of advantages
of pulse gas discharge against a stationary high density of gas discharge plasma, heat action controlling on treated
product, the range of technological processes widening etc. [2].
The investigation of pulse MSS in the regimes of higher discharge currents is stimulated by possibility to
decrease the energy costs on the process of ion sputtering at high discharge current density on a target – transition
ion-atomic interaction to the regime of “heat peaks” [3].
In the paper high-current magnetron sputtering system with arc blowout and electron flow on treated surface
suppression is described. It is investigating the regimes of magnetron sputtering system depending on external
supply circuit parameters, geometrical parameters of electrodes in vacuum conditions.
PROBLEM DEFINITION
At solving the problem of increasing discharge current in planar magnetron sputtering system (MSS) without
transition to arc regime of discharge and suppression of electron flow on treated surface it took into account that in
magnetron discharges the flows of charged particles on substrate led to its addition heating are connected with two
physical reasons. Firstly it is an ordered motion of electron towards substrate at deregulation of magnetic system
MSS; secondly it is a diffusion motion of charged particles at substrate arrangement close or directly on an anode
electrode.
Thus, for charged particles flow decreasing on the substrate (both ordered and diffusion motion), that led to its
addition heating it is necessary to place anode electrode in both sides of arched magnetic field in MSS or from the
side of lesser magnetic field intensity; current-collecting surface of the anode should be placed in the area of arched
magnetic field with the intensity not less than 50 Oe.
In the magnetron discharge at current higher than some critical one which is determined by cathode material and
is in the range of 15-30 A the transition of glow discharge in transverse magnetic field to arc one (the breakdown
phenomena). At that the discharge characteristics sufficiently change. Resistance of the discharge drastically
decreases in hundreds times, discharge current drastically increases and discharge voltage decreases. The form of
current passing from the diffusion distributed along the erosion area transits to flex-like one. On the cathode quickly
moved cathode spots appears, which are the centers of the discharge and create the channel of current passing from
cathode to anode as flex-like ones.
They apply several methods of arc blowout in magnetron discharges. At short time switch off the voltage on the
electrodes and discharge current breaking or at ac voltage supply using of the both situated closely MSS the cathode
spots die. At increasing the distance between the cathode and anode the voltage on the arc increases and cathode
spots die as well.
Thus, for arc blowout (created cathode spots blowout) it is necessary to use the effects of resistance increasing of
discharge gap and discharge current breaking. The elements of vacuum chamber equipment which are at ground
potential should not be the discharge current-collecting i.e. the anode should not be at ground potential and MSS
electrodes (cathode and anode) should be electrically “undone” with substrate holder and vacuum chamber.
EXPERIMENTAL SETUP
The experiments was carried out with standard circle MSS using with sputtered target 110 mm in diameter. The
magnetic field of arched configuration above the target surface was created by permanent magnet system placed
under the target. The maximum intensity of arched magnetic field on the target surface was 300 Oe. The diameter of
the maximum intensity of arched magnetic field was 70 mm. The cathode unit of the MSS was surrounded with
collar electrode which was at floating potential. For this MSS the anode unit with electromagnetic system of arc
blowout and charged particles flows breaking on the substrate was calculated, constructed and created. The anode
unit was situated directly in front of sputtered target MSS and was oriented parallel to it to diameter. The distance
cathode-anode could be varied.

The anode unit consist cylindrical anode electrode 28 mm in diameter, magnetic system and system of
electrically insulated shields 37 mm in diameter. Not shielding parts of the surface of the cylindrical anode 15 mm in
length played role of electron current-collectors of magnetron discharges and was geometrically placed above the
erosion area of MSS. The rest of anode surface was under electrically insulated shields. The magnetic system of
anode unit consisted of 8 cylindrical permanent magnets and it created in current-collecting areas axially
symmetrical arched magnetic field with maximum intensity on the anode surface 200 Oe. The intensity of the
magnetic field exponentially decreased from the anode surface on the distance of 2 cm. The anode electrode was
oriented parallel to sputtered target to diameter such a way that magnetic fields directions of magnetron and anode
unit were coincided.
Thus, probable creation of cathode spots on the sputtered target surface of MSS and discharge transition to arc
regime are prevented from both the additional magnetic field insulation of current-collecting anode surface and the
increasing of current length arc flex at cathode spots motion in the erosion area of the MSS in line of bearing under
the magnetic field action.
For the investigation of developed system in magnetron regime (at discharge voltage about 500 V) with large
currents (about 100 A) the quasistationary pulse supply unit (fig. 1) of capacity type (C1) with thyristor contactor
(D6) with energy resource 700 J was manufactured. The inductance (L1) serve for stable contactor launch and for
pulse duration adjusting of voltage “idling”, which in our experiments was 10-2 sec. Taking into account that the
time of stationary discharge establishment in magnetron is 10-5 sec. one can consider that discharge in MSS at this
voltage pulse parameters is practically stationary. For the second half-period of supply unit voltage cut off at
discharge transition to arc regime the diode (D5) was placed into the scheme. Into the scheme the resistor R1~10-
30 Ω for restriction of magnetron discharge current was placed as well. In process of experiments the discharge
voltage (with the help of high-resistance voltage divider) and discharge current (with the help of Rogovsky coil)
were measured in the wide range of working gas (Ar) pressures p = 8 ⋅10−4 ÷ 5 ⋅10−2 torr .
EXPERIMENTAL RESULTS
The investigations have shown, that depending on distance between cathode and anode and working pressure
value in the chamber the changing of discharge glow regime in MSS takes place.
At lower pressures in the chamber p = 8 ⋅10−4 ÷ 6 ⋅10−3 torr and distance cathode-anode not less than 25 mm the
magnetron regime of discharge glowing is observed. On the fig. 2(a) and fig.

high discharge voltage (on average 400 V) at large currents (40-80 A) talks about that the MSS works in
magnetron regime, i.e. transition to arc regime in this parameters range successfully suppressed.
At increasing of pressure in the chamber up to the values p > 6 ⋅10−3 torr at the same distance cathode-anode
the transition of the discharge to arc regime is observed. Transition of the discharge to arc regime is observed at
decreasing the distance cathode-anode up to the values 15-20 mm as well. On the fig. 3(a) and 3(b) the view of highcurrent
low-voltage arc discharge glow and typical oscillograms of discharge current and voltage are shown.

The discharge voltage and current oscillograms talk that in the moment of voltage loading to cathode-anode gap
in MSS the high-voltage high-current magnetron discharge with the parameters Ud ≈ 900 V , Id ≈ 70 ÷ 80 A is
ignited. However high voltage is saved only during short period of time from the moment of discharge ignition
( ≈ 0.1 ms ) after that voltage breaking up to several tens volts follows and current drastically increases up to 120-
180 А. At that on the surface of the MSS cathode brightly lightening moving along the azimuth cathode spots and
current flexes between the cathode and current-collected surface of the anode visually observed.
SUMMARY
Thus, it has been shown in the work that increasing of the flow of transverse magnetic field between the cathode
and anode of MSS leads to increasing of electrical resistance of gas discharge plasma.
With the aim of maximum value of discharge gap resistance achievement it is worthwhile to create additional
magnetic field with the maximum intensity close to the anode of MSS. Total magnetic flow of cathode and anode
magnetic fields optimally should correspond to minimum discharge glow voltage.
In stationary MSS for periodical discharge current breaking at cathode spots creation and constriction of
discharge current it is worthwhile to use the phenomena of cathode spots moving in transverse magnetic field along
the erosion area with the help of sectioned anode where the current-collected surface of the anode is alternated with
galvanical insulated one along the direction of current flex moving.
REFERENCES
1. V. P. Belevskiy, A. I. Kuzmichov and all, “Pulsed ion treatment and deposition of thin films and coatings”, Kiev: “Znanie”
Ukraini, 1991, p. 23.
2. A. I. Kuzmichov, “Grids for pulsed supply of magnetron sputtering systems”, Proceedings of 7th International Symposium
“Thin films in electronics”, Ioshkar Ola, 1996, pp.237-240.
3. R. Berish, “Sputtering of solid bodies by ion bombardment”, Moscow: Mir, 1984, p. 336.

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