Electrical supply unit for plasma systems

Technical field

The invention relates to an electrical versor supply unit for plasma systems, such as plasma processing or coating devices in which it is to Auftre th of arcs or disruptive breakdown between Elek may electrodes, according to the preamble of patent entitlement. 1

Plasma systems, for the generic electric Supply units are determined, for example, used for sputtering and have an electrical Lei Stung in the order of about a few kW to more than 100 kW. The voltage applied to the electrodes operating tension voltage typically lies in the order of 400 V. course are deviations top or bottom.

In particular, the so-called "reactive" sputtering, the for example for the production of oxide or nitride films is used, problems arise due to the occurrence of discharges and / or the formation of insulating Layers on the conductive target, through which para -university capacitors can form.

In EP 0534068 A2 discloses an apparatus for power supply of Plasma systems described. The current is controlled by a full bridge scarf device connected four semiconductors. In order to limit the current rise through the semiconductor switch on finite values ​​(finite di / dt) is a Series inductance provided. Your connected in parallel a freewheeling diode. For this inductance limita- the current rise while power zen can, the energy needs in the inductor in the switching pauses on Freewheeling diode are degraded. By limiting the current increase through the semiconductor switch is also the increase in current through the plasma chamber and due to the parasitic capacitances and the voltage increase limited to the plasma chamber.

There are a variety of passive and active Scarf tions known, used for extinguishing arcs, which have formed the basis of breakdowns. Allen These circuits have in common that limited hours for a th period from the voltage applied to the voltage electrode is switched. Only by way of example is this, on the US- referenced Patents 5,009,764, 5,015,493 and 5,682,067, to the rest be in explaining each in detail here written details herein by reference.

U.S. Patent No. 5,682,067 describes in the rest of the state of Art from which the formulation of the preamble has been considered the claim 1.

A disadvantage of the known from these publications Circuits is that after switching on the Be operating voltage the system a comparatively long time needed to "sputter full power" again to can.

The same applies if the system called in a asymmetric pulse mode is operated to the formation of insulating layers to prevent the target.

Summary of the Invention

The invention has the object of providing an electrical specify cal supply unit for plasma systems in the after re-applying power to the Electrodes, the system as quickly as possible its full Lei Stung achieved.

An achievement of this object is in Pa tentanspruch 1 indicated. Developments of the invention are the subject of claims 2 et seq.

According to the invention of an electric supply assumed unit, the DC or a DC power source whose output terminals on little least an inductor and a power switch with the electrodes of the plasma unit are connected, and a Circuit for detecting electric arcs or disruptive breakdown which the one at the occurrence of an arc or Punch the switch is actuated such that no more electrical energy is applied to the electrodes.

Starting from such a known Versorgungsein unit, the invention consists in that the Induktivi is ity (s) should be wired with a freewheeling diode (Be), and that the switch is a series switch.

Due to this design, the invention works Supply unit as follows:The switch of the voltage applied to the electrodes elec tric power switches, (hereinafter referred to as Lei breaker called), opens when it detects a Arc current flow between the DC source and the electrodes. The diodes based on connected in the normal operating voltage in the reverse direction are preventing the opening of the circuit breaker that the voltages at the inductances rise and be Farming ken the same time that the current in the inductors only very slowly decreases. If the circuit breaker already after a short time - typically are about a few milliseconds - Switched on again, so is the in the inductors th stored power available immediately, so that the System faster than in the prior art its full achieved performance. The invention Versorgungsein unit has thus upon reconnection of the power scarf ters a current source characteristic.

This means that during the electrical versor invention supply unit, the loss in performance due to the Shutdown of the operating voltage to extinguish the light sheets substantially less than in the prior art.

This invention - in claim 1 mentioned - Basic circuit can under different aspects, the also can be combined, expanded who the:In particular, it is possible in each line, the one Terminal of the DC voltage or direct current source with of the respectively associated electrode, connecting a Induk tivity provide with an associated freewheeling diode. This results in a particularly symmetrical scarf device construction. However, it is possible to use only an inductance to use; in this case is only a one-way diode required.

The switch can, of course, the difference most diverse power switches may be used. In view to the high performance, it is preferable if the Switch is an IGBT.

Even as a power supply, the different Netztei le are used, also as regards the high Performance, however, it is preferred if the DC clamping voltage source is a switching regulator power supply.

In this case, it is advantageous if between the On Combinations of a Gleichspannung- or DC power source Capacitor is connected. This capacitor is used for Avoid voltage spikes caused by the Zulei occur tion inductances in the supply unit can. Furthermore, this capacitor in the time is turned off the power switch, to the full charged open circuit voltage, so that when switching the power switch the full voltage for ignition the plasma is available.

The inventive supply unit can be for use various plasma systems, as example as plasma systems in which one electrode little least one camera arranged in a plasma cathode has, and the other electrode of the housing of the plasma chamber is. The inventive supply unit has In addition, the special advantage that it also Plasma systems can be used, in which at least two separate cathodes are provided, of which each using a series switch with a free wheeling diode wired inductance at one terminal the DC voltage source is connected.

In such systems, for example, between the Cathodes are alternately switched. This has the Advantage that electric arcs, which on the one cathode "in Emergence "are reliable in the comparatively lan are deleted gene period during which other on the Cathode is switched. Of course, it is also possible to simultaneously SPUT of several cathode tern.

In one development of the invention is between the Electrode terminals and the pairs of electrodes a diode connected. The function of this diode is the following explained:When the circuit breaker opens, the voltage at polt the lead inductances to the plasma chamber in a way that without further circuit measures voltage spikes would result. The ge between the electrode terminals switched diode shorts this voltage, so that the from the lead inductances stored energy is built.

Furthermore, it is possible to use a LC element parallel to the switch diode, which as a passive element deletion of the arc supports.

Particularly preferred, it is, however, if the deletion of the Arc supported by active circuit elements becomes:To this end, in series with the diode, a capacitor ge be switched. Between cathode terminal and the Verbin grounding point diode / capacitor is then a further Seri limit switch connected. is through this circuitry viewed from the line inductance and the current flowing Current resulting energy when opening the power scarf ters transferred as a voltage in the capacitor. After egg including a short delay, this voltage across the white applied direct series switch to the electrodes, so that the arc considerably faster than in a passivating ven circuit is cleared.

To even with small line inductances or small Currents a correspondingly large inverted voltage to Delete to obtain, in addition, an inverse voltage source are provided.

This inverse voltage source may, in particular a (Auxiliary) be -Gleichspannungsquelle whose negative pole the anode and whose positive terminal through a forward diode connected to the one terminal of the further Se rien switch is connected.

In any case, it is preferred if the circuit for Electric arc detection except the power switch also the further switch activates.

The circuit for electric arc detection can we Evaluating least one of the following criteria:

<ul><li>- Voltage drop,</li><li>- Exceeding the maximum voltage limit,</li><li>- Below the minimum voltage limit</li><li>- Rapid current rise,</li><li>- Exceeding the maximum current limit.</li></ul>

Further, a control unit, which in particular Be be an integral part of the circuit for electric arc detection can be provided which periodically applied to the electric the applied voltage off and preferably switches. Becomes the voltage applied to the electrodes on a regular basis for reversed the moment, so can the emergence of Arcs are substantially reduced or can Arcs deleted already in the development who the.

Due to the inventive design, the a rapid achievement of performance results, which leads rule even reversal of the voltage only to a very low Reduction of the sputtering power, where the time duration, during which the voltage applied to the electrodes to is switched, is much shorter than the time period, during which a plasma operation is performed. furthermore has the time duration during which the voltage switched is, of course, also be so short that the current in the Circle "inductance / freewheeling diode" is stored.

The frequency with which the control unit to the Elek electrodes applied voltage off or switches, may be up to 100 kHz.

Brief Description of Drawing

The invention is described below with reference to the described drawings, showing in:

<b>Fig.</b> 1 the circuit of a first embodiment the invention,

<b>Fig.</b> 2 is a voltage / time diagram to illustrate the Operation of the in <b>Fig.</b> 1 shown Scarf Maintenance,

<b>Fig.</b> 3 shows the circuit of a second Ausführungsbei clearance of the invention,

<b>Fig.</b> 4 is a voltage / time diagram for explaining the Operation of the in <b>Fig.</b> 3 shown Scarf Maintenance,

<b>Fig.</b> 5 is a voltage / time diagram for explaining the Operation of a modification of the in <b>Fig.</b> 3 shown circuit,

<b>Fig.</b> 6, the circuit of a third Ausführungsbei clearance of the invention, and

<b>Fig.</b> 7 is a voltage / time diagram for explaining the Operation of third Ausführungsbei , game.

Illustration of exemplary embodiments

<b>Fig.</b> 1 shows a first embodiment of the inven tion. The power supply unit has a Schaltreg ler PSU <b>1</b> on which, for example (ie without Be of generality), a DC voltage of about 400 V supplies. The negative output terminal A of the network part <b>1</b> is via an inductor L1 and a as Seri limit switch designed breaker with a V3 Cathode K in a plasma chamber <b>2</b> connected whose housin se is grounded. The series switches<b>1</b> is at the gezeig th embodiment, an IGBT. The positive output connection A + of the power supply <b>1</b> is via an inductance L2 with the housing of the plasma chamber <b>2</b> connected. This is symbolically designated GND.

Parallel to the inductors L1 and L2 are Invention switched according diodes V1 and V2, the poled such are that they block the plasma operation.

Furthermore, between the output terminals A and A + a Capacitor C1. Between the cathode terminal and GND is a diode V4 connected to the Plasmabe poled operating in the reverse direction.

Furthermore, a circuit <b>3</b> for detecting Lichtbö gen or disruptive breakdown provided which switches the series V3 controls via the output terminal "Gate". to a Arc - also called Arc - to realize measures the circuit <b>3</b> the flowing current I and the voltage U and evaluates the measured variables according to the following criteria out:

<ul><li>- Voltage drop,</li><li>- Exceeding the maximum voltage limit,</li><li>- Below the minimum voltage limit</li><li>- Rapid current rise,</li><li>- Exceeding the maximum current limit.</li></ul>

Upon detection of an arc of power scarf is ter V3 of the circuit <b>3</b> opened so that the current flow between the power supply <b>1</b> and the electrodes of the Plasmakam mer <b>2</b> is interrupted. Opening the power scarf ters polt the voltage on the lead inductances the plasma chamber <b>2</b> around; to avoid that this tension to voltage spikes leads, the electrodes through the diode V4 shorted and the Zuleitungsinduktivitä th stored energy degraded. The diodes V1 and V2 prevent, firstly, that the voltages at the Indukti activities L1 and L2 when opening of the circuit breaker at rise and simultaneously cause the current in the Inductances decreases only very slowly. The inductors th L1 and L2 can be magnetically coupled. Of the Capacitor C1 is used to prevent voltage spikes, which may occur through the lead inductances.

In the following, the operation of the in <b>Fig.</b> 1 ge showed electrical supply unit with reference on <b>Fig.</b> 2, in which a voltage / time diagram Darge represents is described in more detail:At time T1, the voltage U breaks due to a Arc on for an arc or breakdown typical voltage U_ARC on. After an adjustable Verzö delay time T1-T2 of the switches V3 is opened and the Power supply interrupted. After an adjustable light arc break T2-T3, the switch V3 is CLOSED again Sen, the voltage rises to the ignition voltage U_ZÜND at and breaks back to the operating voltage U_PLASMA back.

By inventively provided freewheeling diodes V1 and the generator output current is V2 at the time of Shutdown stored so that upon reconnection the original operating state very quickly he enough is.

<b>Fig.</b> 3 shows a modification of the in <b>Fig.</b> 1 shown Embodiment. Here, the same parts as in<b>Fig.</b> 1 provided with the same reference numerals and so on renewed presentation will be omitted.

In this embodiment, is in series with the diode V4, a capacitor C2 connected. Between the terminal the cathode K and the connection point of diode V4 / Kon capacitor C2, a further series switch V5 is connected, likewise by the circuit <b>3</b> via the output connection gate <b>2</b> is driven.

Further optional an inverse voltage source provided be seen that an (auxiliary) -Gleichspannungsquelle U1 having, typically a voltage of about 30 V supplies. The negative terminal of the DC voltage source U1 is connected to the anode, while the positive pole of the DC voltage source U1 via a geschal in forward direction tete diode V6 to one terminal of the other series switch V5 is connected.

In the following, the operation of the in <b>Fig.</b> 3 ge showed the second embodiment with reference to <b>Fig.</b> 4 explained in more detail, which is a voltage / time diagram shows.

When an arc occurs (time point T1) breaks the voltage of the plasma voltage U_plasma on the Arc voltage U_Arc together. Then open the circuit <b>3</b> the power switch V3. By the Diode V4 connected in series, the capacitor C2 is resulting from the lead inductance and the current Energy transferred as a voltage in the capacitor C2. To the Time T2, these tensions as inverse voltage the electrodes of the plasma chamber <b>2</b> applied so that the Arc much faster than without active extinction is deleted. The optional voltage source U1 , the applied inverse voltage can be increased.

Provides you the circuit <b>3</b> with an additional pulse generator, then the voltage applied to the plasma chamber Tension regularly for the moment reversed who the. Thereby, the probability for the de genesis of arcs can be substantially reduced or Arcs can be deleted again already in the development will.

In addition, prevents the reactive sputter form tern oxide layers on the target; continue Kings NEN oxidized targets are freigesputtert.

<b>Fig.</b> 5 schematically shows the voltage variation for these Modification of the in <b>Fig.</b> 3 shown Ausführungsbei , game. The heart rates can vary depending on used Circuit breaker be up to 100 kHz.

<b>Fig.</b> 6 shows the circuit of a third Ausführungsbei Game of the invention in which in the plasma chamber <b>2</b> two Cathode K1 and K2 are arranged, which each have their own Breaker V3 and V5 and V4 and V6 diodes zugeord are net.

By simultaneously switching on the power switch V3 and V5 work the two cathodes in parallel operation. If the two switches are alternately turned on, , by variations in the turn-effective Performance of the cathode can be controlled. There are Shift frequencies up to several kHz.

<b>Fig.</b> 7 shows a voltage / time diagram by the al ternierende switching of the two switches schematically is shown. Of course, also more than two cathodes are used.

The invention is described above with reference to exemplary embodiments play without limiting the generality described been. In particular, the various self-sheep th the embodiments combined together who the:Thus, it is possible to make the pulsed operation, the active deletion arcs and switching between two or more Cathode to combine with each other.