WO2011063787A1

WO2011063787A1 - Self-balancing rf plasma power supply

Info

Publication number: WO2011063787A1
Application number: PCT/DE2010/001346
Authority: WO
Inventors: Rolf Merte
Original assignee: Hüttinger Elektronik Gmbh + Co. Kg
Priority date: 2009-11-25
Filing date: 2010-11-16
Publication date: 2011-06-03
Also published as: DE102009054449A1

Abstract

The invention relates to an RF process energy supply (1) having an output impedance (10) for connecting to a plasma excitation arrangement (5) having a dynamic plasma impedance (6), the RF process energy supply comprising: a connection (3) to an electricity supply network (2), at least one direct-current supply (4) connected downstream of the connection (3), at least one RF inverter (7) connected downstream of the direct-current supply for producing RF power having frequencies greater than 3 MHz, an electronically variable impedance adaptation circuit (8) connected downstream of the RF inverter, an output connection (9) that is connected downstream of the impedance adaptation circuit and to which the plasma excitation arrangement is connected, the RF process energy supply being characterized in that the output impedance of the RF process energy supply can be set to the value of the plasma impedance or has a magnitude less than 30 Ω during a plasma excitation, and the RF inverter is a free oscillator.

Description

Self-balancing RF plasma stromal sauna

The invention relates to an RF process energy supply for connection to a plasma excitation. An RF plasma excitation is usually done from one or more RF power supplies. RF stands for "radio-frequency" and in plasma technology it usually means frequencies higher than 3 MHz, RF power supplies often become RF in plasma technology

Generators called, they provide the plasma process with process energy, so the term process energy supply is used as a synonym. They usually have an output impedance of 50 Ω. This is due to the fact that the commercial cable and plug contacts for this

Impedance are designed. When generating the RF voltage within the RF power supply, the impedance is initially not usually 50 Ω but lower in magnitude. This absolute low impedance is converted within the RF power supply with a fixed impedance conversion to a 50 Ω output impedance. The energy is transferred to the RF plasma process on the 50 Ω cables. The RF plasma process itself usually also has a much lower impedance than 50 Ω, in addition, this impedance is variable. In order to match the 50Ω to the impedance of the RF plasma process, an impedance matching network (matchbox) is usually used, which is automatically tunable. Is known

for example from US5654679, to change the frequency to achieve a fixed impedance matching network matching. For this purpose, for example, the frequency is changed via a control in order to increase the forward power P, or to reduce the reverse power P _r . A complex regulation is required for this, which is also superimposed with other regulations, which can lead to stability problems. From DE3519489 an example of a free-running oscillator is known, for use in induction heating.

The object of the invention is to provide an improved RF process power supply with increased matching speed and increased reliability for increased reliability of the plasma process.

The object is achieved by an RF process energy supply having an output impedance for connection to a plasma excitation arrangement with a dynamic plasma impedance, the RF process energy supply comprising: connection to a power supply network,

at least one DC power supply connected downstream of the terminal, at least one RF inverter connected downstream of the DC power supply for generating RF power with frequencies greater than 3 MHz

a downstream of the RF inverter electronically variable

Impedance matching circuit,

an output terminal connected downstream of the impedance matching circuit to which the plasma excitation array is connected, the

Output impedance of the RF process power supply is adjustable to the value of the plasma impedance and / or during the plasma excitation magnitude not equal to 50 Ω, in particular less than 30 Ω, and wherein the RF inverter is an RF cantilever.

The component-intensive impedance transformation of inverter impedance to 50 Ω and subsequent back transformation to plasma impedance is avoided in this way. This makes the RF process energy supply cheaper and cheaper

more reliable and shows an accelerated adaptation behavior. For the

Operator becomes the whole process more reliable.

With RF cantilever is meant a circuit arrangement that automatically operates without additional external control to one of the output impedance

adjusted frequency. Such a cantilever arrangement has particular advantages in use together with an electronically variable impedance matching circuit. With an electronically variable

Impedanzanpassungsschaltung is meant an impedance matching circuit whose reactances so usually capacitors and / or inductors can be changed electronically, that means without mechanical drives. Such Electronically variable reactances can be gradually adjustable. The RF cantilever adjusts itself then within a period or within a few periods on a modified impedance matching circuit and runs within a very short time optimally adjusted. With the combination of RF cantilever and electronically variable impedance matching circuit, which adapts directly to the plasma impedance without adjustment to a 50 Ω

Interim impedance results in a variety of advantages: Thus, can be dispensed with a measurement and additional control for frequency adjustment. Costly components can be dispensed with. The fitting speed increases. From an operator's point of view, increased process stability results. By saving components also reduces the risk of failure of these components, which further increases the reliability. With RF inverters are

Circuitry that generates high power RF signals from low power RF signals. Since the RF inverters of this invention are always RF cantilevers, the low power RF signals are generated by self-resonance, which depend on the one connected to the RF inverter

Impedance adjusted, so the impedance matching circuit. Such inverters can be used to switch DC power to RF power

Transistors or tubes have. When using transistors that operate in switching mode.

To implement the electronically variable impedance matching individual reactances can be switched by means of PIN diodes.

An RF power supply can be located in close proximity to the

Plasma excitation be arranged. Reflections on poorly adapted

Connections and cables can be avoided.

If an RF process power supply with a short or long

Connecting line is connected to a plasma excitation arrangement, can be provided in the process energy supply a Ausgleichs reactance for this line, e.g. a capacity to compensate for a line inductance. Several RF process power supplies may be connected to a plasma excitation via multiple coupling electrodes or antennas.

At the output terminal sensors can be provided for determining voltage and current and the phase between voltage and current phase as well as an evaluation device for determining the RF power and / or plasma impedance. The high-resolution real-time measurement of current, voltage and Phase between current and voltage results in an increased control speed and process reliability over the conventionally used measurement of forward and reverse power.

There may be sensors for determining the RF power and / or

Plasma impedance to be provided to the DC power supply. The measurement of RF power and / or plasma impedance on the DC voltage signals simplifies the design and saves costly components and costly calibration.

The process power supply may include a controller for controlling the RF power to the DC power supply. Especially at

Inverters that operate in switching mode, such an arrangement can be provided.

The object is also achieved by RF power supply techniques for supplying a RF power plasma excitation array, the method comprising the steps of:

Absorption of electrical power from a power supply network,

Rectification of the electrical power from the power supply network into a DC power,

Converting the DC power into an RF power with a frequency greater than 3 MHz by means of an RF inverter with an RF inverter impedance,

Conversion of the RF inverter impedance into an output impedance by means of an electronically variable impedance matching circuit,

Supplying the RF power through the impedance matching circuit via an output terminal to a plasma excitation,

wherein the output impedance amounts to values not equal to 50 Ω,

'is set in particular less than 30 Ω and the frequency of a RF

Inverter automatically adjusts to the impedance matching circuit.

By adapting the frequency to the impedance matching circuit is meant an automatic self-regulation of the frequency of the RF inverter to an optimum operating frequency which is close to the resonance frequency of the RF

Impedanzanpassungsschaltung or the inverter circuit may be together with the impedance matching circuit. This self-regulation is usually done in less than one period or less

Periods.

Such a method has the advantages described above. The output impedance can be controlled directly on the plasma impedance. In the method, the RF power and / or the plasma impedance can be made from a measurement of the current, the voltage and the phase between current and voltage.

In the method, the RF power and / or the plasma impedance can be determined by measuring signals exclusively at terminals of the DC energy.

In the method, a regulation of the RF power can be done by controlling the DC power.

Other features and advantages of the invention will become apparent from the

The following description of exemplary embodiments of the invention, with reference to the figures of the drawing, the essential features of the invention shows, and from the claims. The features shown there are not necessarily to scale and presented in such a way that the features of the invention can be made clearly visible. The different features can each individually for themselves or to several in any

Combinations in variants of the invention be realized.

In the schematic drawing embodiments of the invention are illustrated and explained in more detail in the following description. Show it :

Fig. 1 Schematic representation of a process energy supply with a

Plasma excitation arrangement

FIG. 1 shows an RF process energy supply 1 with an output impedance 10 for connection to a plasma excitation arrangement 5 with a dynamic plasma impedance 6. At the RF process power supply 1 there are a connection 3 to a power supply network 2, and an output connection 9 to which the plasma excitation system 5 is connected. For example, any interconnector reactance 16 may be an inherent inductance or capacitance, or a combination of both. It may be compensated by an optional equalization reactance 15 which may be located in the RF process power supply 1. If the RF process power supply 1 directly to the plasma excitation arrangement. 5 connected or at least arranged in the immediate vicinity, the Ausgleichs reactance 15 can be omitted.

The DC power supply 4 is connected downstream of the terminal 3. It may be a regulated or unregulated DC power supply, preferably it can be controlled with the control device 14 and takes place in this way one

Control or regulation of the RF power.

Optionally, sensors 13 are provided for connection to any connection in the DC power supply. Hereby the impedance and / or the power can be determined. This measurement can also be used to control the power. The DC power supply 4 is followed by an RF inverter 7 for generating RF power. The RF Inverter is a cantilever that varies its frequency depending on it

connected circuit adjusts. It has an RF inverter impedance 17, which is indicated by an arrow in FIG. The RF inverter 7 is followed by an electronically variable impedance matching circuit 8, which may have electrically variable capacitances. It can also have electrically variable inductances. Electrically variable means in this

Connection variable by electrical signals without the aid of mechanical drives. One possibility is the gradual connection of inductors or capacitors via PIN diodes or comparable means. One possibility is also the use of capacitance diodes, whose capacitance is controlled by a coupled DC voltage. Another possibility is to influence inductors with saturable nuclei via an injection of magnetic fields, e.g. by means of a DC-powered coil. In the area of the impedance matching circuit 8, preferably after the impedance matching circuit 8 and before the output terminal 9, there is an optional current and voltage sensor 11. Connected to it is an evaluation device 12, which determines the power and / or the plasma impedance. This can optionally be supplied to the control 14. This can also be a connection to the electrically variable

Impedance matching circuit 8 have. Likewise, the controller 14 may have a connection to the electrically variable impedance matching circuit 8.

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Claims

Claims:

An RF power supply (1) having an output impedance (10) for connection to a plasma excitation array (5) having a dynamic plasma impedance (6), the RF power supply comprising: terminal (3) to a power grid (2),

at least one of the connection (3) downstream

DC power supply (4),

at least one of the DC power supply downstream RF inverter (7) for generating RF power with frequencies greater than 3 MHz downstream of the RF inverter electronically variable

Impedance matching circuit (8),

one of the impedance matching circuit downstream

Output terminal (9) to the plasma excitation arrangement

is connected, characterized in that the output impedance of the RF process power supply is adjustable to the value of the plasma impedance or during a plasma excitation magnitude not equal to 50 Ω, in particular less than 30 Ω, and that the RF inverter on

Cantilever is.

2. RF process energy supply according to claim 1, characterized in that at the output terminal measuring sensor (11) for determining

Voltage and current and the phase between voltage and current as well as an evaluation device (12) are provided for determining the RF power and / or plasma impedance.

3. RF process energy supply according to one of the preceding claims, characterized in that sensor (13) for determining the RF power and / or plasma impedance at a terminal of the

DC power supply are provided.

4. RF process energy supply according to one of the preceding claims, characterized in that a control device (14) for

Regulation of the RF power is provided to the DC power supply.

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5. RF process energy supply according to one of the preceding claims, characterized in that in the RF process energy supply

Equalization reactance (15) to compensate for

Verbindungsleitungreaktanzen (16) between the output terminal and Plasmanregungsanordnung is provided.

6. Method for RF process energy supply for supplying a

A plasma excitation assembly with RF power, the method comprising the steps of:

Recording electrical power from a power grid, rectifying the electrical power from the power grid into a DC power,

Conversion of the DC power into an RF power with a frequency greater than 3 MHz by means of an RF inverter with an RF inverter impedance (17),

characterized in that the output impedance to values

in terms of magnitude not equal to 50 Ω, in particular less than 30 Ω is set and that the frequency of an RF inverter automatically to the

Adjusts impedance matching circuit.

7. Method for RF process energy supply for supplying a

A plasma excitation assembly with RF power, the method comprising the steps of:

Conversion of an RF inverter impedance into an output impedance by means of an electronically variable impedance matching circuit,

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characterized in that the output impedance is set to values of plasma impedance and that the frequency of an RF inverter automatically adapts to the impedance matching circuit.

8. The method according to any one of claims 6 or 7, characterized in that the RF power and / or the plasma impedance from a measurement of the current, the voltage and the phase between current and voltage.

9. The method according to any one of claims 6 or 7, characterized in that the RF power and / or the plasma impedance are determined by measuring signals exclusively at terminals of the DC energy.

10. The method according to claim 9, characterized in that a regulation of the RF power takes place by the regulation of the DC energy.

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