DE4138793A1 - Process and appts. for coating substrate - uses current source connected to cathodes in evacuated coating chamber - Google Patents

Abstract

Process for coating a substrate (7), esp. with non-conducting layers, of electrically conducting targets (3,4) in reactive atmos., uses a current source (12,13,14) connected to cathodes (1,2) in an evacuated coating chamber (15), which act electrically together with the targets (3,4) that are then sputtered. The sputtered particles form on the substrate (7). The novelty is that the ave. freq. voltage is chosen at a lower figure that the plasma discharge occurs at each zero througput of change in voltage and is ignited in each semi-wave of voltage change as soon as the voltage of the transformer (12) rises sufficiently. The exits (12a,12b) of the sec. coil of the transformer (12) are connected to one of the cathodes (1 or 2), the transformer being connected to a generator (13). Supply lines (20,21) are connected via a branch line (22), in which a resonant circuit is arranged. Each of the lines (20,21) is connected not only via a first network (16 or 17) to the coating chamber (15) but also via a corresponding second network to each anode (5 or 6). ADVANTAGE - During the coating process using magnetron sputtering source in reactive atmos., arcs disappear or the tendency or arcs to appear is reduced.

Description

The invention relates to a method and a device for coating a substrate, especially with elec trically non-conductive layers of electrically conductive targets in a reactive (e.g. oxidizing) atmosphere, consisting of a power source that is included in an evaku arranged coating chamber, magnets closing cathodes, which is electrically connected to interact with the targets that are on the substrate knock down, being electric from each other and from the Sputter chamber separate anodes are arranged which in a plane between the cathodes and the substrate are seen.

It is already an atomizing device for manufacturing known thin layers (DD 2 52 205): consisting of a magnet system and at least two above it  th electrodes made of the material to be atomized, where these electrodes are electrically designed so that they are alternately cathode and anode of a gas discharge. The electrodes are sinusoidal for this purpose AC voltage of preferably 50 Hz connected.

This known atomizing device is intended especially for the deposition of dielectric layers by reactive Atomization may be suitable. By operating the facility tion with about 50 Hz should be avoided that it Tinsel formation on the anode and in the case of metal stratification to electrical short circuits (so-called Arcs) is coming.

In another already known device for opening dust a thin film at which the speed bringing down layers of different mate rialien is adjustable (DE 39 12 572), so too extreme to arrive at thin layer packages is at least two different types of cathode side provided Counter electrodes arranged.

Furthermore, there is an arrangement for depositing a metal alloy known with the help of HF cathode sputtering (DE 35 41 621), in which two targets alternately are controlled, the targets being the metal components of the metal alloy to be deposited, however, with under different proportions included. The substrates are closed arranged for this purpose on a substrate carrier by a drive unit during the atomization process in Rotation is set.  

Through a previously published publication (DE 38 02 852) it is also known at a facility for the Coating a substrate with two electrodes and at least one material to be atomized layered substrate between the two electrodes in to arrange a spatial distance and the AC half waves as low-frequency half-waves with essentially to choose the same amplitudes.

According to another previously published document (DE 22 43 708) is a method for generating a Glow discharge known with one in a working gas attached electrode assembly to which an operating voltage is applied, the process by the Generation of a magnetic field, which together with the elec Trodenanordnung at least one trap to hold practically everything emitted by the electrode arrangement Results in electrons, one to ionize the work gases have sufficient energy. For this procedure finds an electrode arrangement in which the Electrodes are provided in pairs. In particular be this publication also writes hollow electrodes in their Inside a glow discharge can be generated, the Electrodes are designed as tubular shells.

Furthermore, a method and a device are described in an older, not previously published patent application (P 41 06 770.3) for the reactive coating of a substrate with an electrically insulating material, for example with silicon dioxide (SiO ₂ ), consisting of an alternating current source which is associated with in a coating chamber arranged magnets including cathodes are connected, which cooperate with targets, two floating outputs of the AC power source are each connected to a cathode carrying a target, both cathodes are provided in the coating chamber next to each other in a plasma space and to the opposite substrate each about have the same spatial distance. The effective value of the discharge voltage is measured by a voltage rms value connected via a line to the cathode and fed as a DC voltage to a controller via a line which controls the reactive gas flow from the container into the distribution line via a control valve so that the measured voltage with a target voltage match.

Finally, there is a device for reactive coating a substrate in an older one, not pre-published light patent application described (P 41 36 655.7; Zu sentence for P 40 42 289.5), in which one is electrically powered by the Vacuum chamber separate, designed as a magnetron cathode te, from two electrically separated parts existing cathode, in which the target body with Yoke and magnets as one part - under intermediate switching a capacitance - to the negative pole of a DC power supply and the target as that other part via a line and with interposition a choke and one of these parallel opposites stood connected to the power supply and being the target has an additional capacity with the positive pole the power supply and connected to the anode which in turn - with the interposition of a resistor - to ground, in series with the low induction Kapa an inductance in the branch line to the contrary stood and turned on to the throttle and the value for  the resistance typically between 2 KΩ and 10 KΩ lies.

This older device is already designed so that they are the vast majority of those during a Beschich arcs suppressed and the Energy of the arcs lowers and the re-ignition of the plas mas improved after an arc.

The present invention is based on the object de, which during the coating process by means of Magne tronsputter source occurring in a reactive atmosphere Make arcs disappear as completely as possible or already in a phase of the process in which the inclination to form an arc increases to recognize this tendency and counteract it. This stabilization of the sput The process should also be particularly insensitive against water vapor residues in the recipient.

In particular, the behavior of the device should the tendency to form arcs for such procedures that are suitable for coating glass slices of metallic conductive targets in reactive (e.g. oxidizing) atmosphere non-conductive layers to separate.

This object is achieved according to the invention by a method ren resolved where the medium frequency voltage is so low is dimensioned so that the plasma discharge at every zero passage of AC voltage goes out and in everyone Half wave of the AC voltage re-ignites when the Voltage of the transformer has risen sufficiently, why the two outputs of the secondary winding of - under  Interposition of a choke coil - with an agent frequency generator connected transformer each a cathode connected via supply lines are connected to each other via a branch line into which an oscillating circuit, preferably a coil, and a capacitor are turned on, each of the two supply lines each via both the DC potential setting towards earth first network with the coating chamber as well a corresponding second network with the respective Anode are connected.

According to the invention, a device is provided in which the outputs of the secondary winding one - under intermediate switching a choke coil - with a medium frequency generator connected transformer (via Ver supply lines connected to one of the cathodes are, the supply lines via a branch tion are interconnected, in which a vibration circuit, preferably a coil, and a capacitor are switched, and being each of the two supply lines each have a DC voltage First network that sets potential to earth with the coating chamber as well as an equivalent appropriate second network with the respective anode are bound.

According to the invention, the important thing is the cathodes "soft" to ignite what happened with the help of a choke can between the transformer and Mittelfre sequence generator is switched on. Furthermore, one Swinging arrangement provided between the cathodes can be made to vibrate by an arc and the  clears the arc when swinging. The resonance of the The resonant circuit must be a multiple of the work frequency sequence of the arrangement.

The invention allows a wide variety of designs opportunities to; one of them is in the attached drawing voltage, which shows the circuit diagram of a device, shown schematically in more detail.

There are two cathodes 1 , 2 fed from the medium frequency generator 13 with sinusoidal alternating current of the frequency of 40 kHz in the coating chamber 15 so that the cathodes alternately represent the negative and positive poles of the sputtering discharge.

In the coating chamber 15 , two magnetron cathodes 1 , 2 are arranged so that a plasma can be ignited between the two cathodes. The cathodes are oriented such that the surfaces of the targets 3 , 4 arranged on the cathodes lie in one plane and parallel to the plane of the substrate 7 or are arranged at an angle to one another and to the substrate plane.

A distance A is maintained between the targets 3 , 4 and the substrate plane. In this space, the electrodes 5 , 6 are arranged, which are connected via the electrical networks 8 and 9 to the cathodes 1 and 2 in the points 10 and 11 respectively.

In the connection points 10 and 11 of the supply lines 20 , 21 , the cathodes 1 and 2 are also connected to a connection 12 a, 12 b of the secondary winding of the transformer 12 . This transformer 12 receives its power from the intermediate frequency generator 13 in which an output terminal 22 of this center frequency genes rators 13 to one terminal of the choke coil 14, the other output terminal 23 of the medium-frequency generator 13 to a terminal 12 c of the primary winding of the transfor mators 12 and the other terminal 12 d the primary winding of the transformer 12 with the second terminal of the Dros selspule 14 are connected.

The connection points 10 and 11 are also still connected to the networks 16 and 17 . The respective second connection 24 , 25 of the networks 16 , 17 is connected to the coating chamber 15 . At the point of connection 10 , a connection of a coil 19 is ruled out, the second connection of which is connected to a connection of the capacitor 18 . The second terminal of the capacitor is connected to node 11 via the device 22 line 22 .

The networks 8 , 9 and 16 , 17 consist of series circuits of diodes, resistors and capacitors and set a total of the DC potential against the earth (ground).

In the arrangement described above, the medium frequency generator 13 generates a sinusoidal AC voltage, which is so high-voltage with the transformer 12 that the voltage range is adapted to the working voltage of the magnetron cathode 1 , 2 . The circuit described cathode 1 , transformer 12 to cathode 2 implies that there is a galvanic connection between the two cathodes, into which the AC voltage is induced via the transformer 12 . This measure ensures that at one point in time the cathode 1 forms the negative pole, ie the sputtering part of the discharge, and cathode 2 the positive pole of the discharge. At another point in time, cathode 1 forms the positive pole of the discharge, and cathode 2 is the negative pole and sputtered with it.

The frequency of the medium frequency voltage is chosen to be so low that the plasma discharge extinguishes with every zero crossing of the AC voltage. It reignites in each half wave of the AC voltage as soon as the voltage at the transformer 12 has risen sufficiently.

This interplay ensures that the discharge is always a bare surface by sputtering as a positive pole finds. If one cathode serves as a positive pole, it becomes from the other cathode sputtering at that moment non-conductive layers. The alternating frequency must should now be chosen so high that the occupancy is insignificant remains for the trial.

Since the physical mechanism is identical to DC sputtering, arcs also occur, of course. But in addition to the conditions on the target surface, the formation of an arc is also linked to time, current and potential conditions (if the alternating frequency is chosen so high that the polarity changes again before the arc was able to form). The choke 14 causes a delay in the current rise both in the ignition and in the formation of the arcs. The resonant circuit formed from the coil 19 and the capacitor 18 is set to a frequency which is substantially higher than the working frequency - approximately 50 times. Should an arc form, this resonant circuit swings and gently causes an additional change in the polarity of the cathodes, so that the arc disappears immediately. The networks 8, 9 and 16, 17 ensure that the potentials of the electrodes 5, 6 and the coating chamber 15 are held so that low field strengths occur in the chamber 15 and thus the arc formation also delayed. The practical freedom from arc is now achieved by combining these measures: 2 galvanically connected cathodes, frequency, choke, networks for potential setting.

• An optimum at 40 kHz was achieved for the working frequency found. The application of frequencies deviates from 40 kHz in the range from 8 kHz to 70 kHz is at Acceptance of loss of quality conceivable.
• An arrangement can be used instead of single-phase alternating current used with multi-phase (three-phase) alternating current will.
• The transformer 12 can be provided with several secondary windings, so that several pairs of cathodes are operated.
• The cathodes can be arranged next to each other instead
  • - nested,
  • - roof-shaped over the substrate,
  • - opposite with openwork substrate in the middle,
  • - be spatially distributed like a quadrupole.
• The design of the cathodes used can be in addition to the planar magnetron
  • - an intermediate pole target,
  • - a tubular magnetron,
  • - a torus magnetron
• be.

Reference list

1 cathode
2 cathode
3 target
4 target
5 anode, electrode
6 anode, electrode
7 substrate
8 electrical network
9 electrical network
10 connection point, connection point
11 connection point, connection point
12 transformer
12 a, 12 b terminals
12 c, 12 d terminals
13 medium frequency generator
14 inductor
15 coating chamber
16 network
17 network
18 capacitor
19 coil
20 supply line
21 supply line
22 branch line
23 output terminal
24 connection
25 connection
26 output terminal

Claims (2)

1. A method for coating a substrate ( 7 ), in particular with non-conductive layers, of electrically conductive targets ( 3 , 4 ) in a reactive (z. B. oxidizing) atmosphere, consisting of a current source ( 12 , 13 , 14 ), which is connected to a cathode ( 1 , 2 ) arranged in an evacuable coating chamber ( 15 ), magnets, which cooperate elec trically with the targets ( 3 , 4 ), which are atomized and whose dusted particles are on the substrate ( 7 ) precipitate, being separated from each other and from the sputtering chamber ( 15 ) separate anodes ( 5 , 6 ) are arranged, which are provided in a plane between the cathodes ( 1 , 2 ) and the substrate ( 7 ), characterized in that the Medium frequency voltage is chosen so low that the plasma discharge goes out at every zero crossing of the AC voltage and re-ignites in every half cycle of the AC voltage as soon as the voltage of the transformer ( 12 ) is sufficient is increased, which is why the outputs ( 12 a, 12 b) of the secondary winding of the interposing selector coil ( 14 ) with a medium frequency generator ( 13 ) connected transformer ( 12 ) each via supply lines ( 20 , 21 ) to one of the cathode ( 1 and 2 ) are connected, the supply lines ( 20 , 21 ) are connected to one another via a branch line ( 22 ), into which a resonant circuit is switched on, and each of the two supply lines ( 20 , 21 ) is both via a setting the DC voltage potential to earth of the first network ( 16 or 17 ) with the coating chamber ( 15 ) and via a corresponding second network ( 8 or 9 ) with the respective anode ( 5 or 6 ) is connected. 2. Device for coating a substrate ( 7 ), in particular with non-conductive layers, of electrically conductive targets ( 3 , 4 ) in a reactive (e.g. oxidizing) atmosphere, consisting of a current source ( 12 , 13 , 14 ), which is connected to a cathode ( 1 , 2 ) arranged in an evacuable coating chamber ( 15 ), magnets, which cooperate elec trically with the targets ( 3 , 4 ), which are atomized and whose dusted particles are on the substrate ( 7 ) deposit, wherein two anodes ( 5 , 6 ) electrically separate from one another and from the sputtering chamber ( 15 ) are arranged, which are provided in a plane between the cathodes ( 1 , 2 ) and the substrate ( 7 ), characterized in that the two outputs ( 12 a, 12 b) of the secondary winding - with the interposition of a choke coil ( 14 ) - with a medium frequency generator ( 13 ) connected transformer ( 12 ) each to a cathode ( 1 or 2 ) via Ve Supply lines ( 20 , 21 ) are connected, the two lines ( 20 , 21 ) being connected to one another via a branch line ( 22 ) into which an oscillating circuit, preferably a coil ( 19 ), and a capacitor ( 18 ) are switched on , and wherein each of the two supply lines ( 20 , 21 ) in each case both via a first network ( 16 or 17 ) with the coating chamber ( 15 ) which sets the direct voltage potential with respect to earth, and also via a corresponding second network ( 8 or 9 ) the respective anode ( 5 or 6 ) is connected.