EP2642833A2 - Device and method for generating a plasma - Google Patents

Abstract

The device (200) has a coupling unit (231) for energy introduction (251), and another coupling unit (232) for energy extraction (252). A resonator (201) comprises waveguides (211-213) operatively connected with a microwave plasma source (241) that is designed as a hollow space. Each coupling unit is in an energy- and/or signal-carrying operative connection with the waveguides. An active element (261) supplies energy to the resonator and is operatively connected with the coupling units. The source is partially integrated into a section of the waveguides that extends between the coupling units. The active element includes a transistor. An independent claim is also included for a method for generating a plasma.

Description

The present invention relates to an apparatus and a method for generating a plasma.

State of the art

The present invention relates to plasma processes using microwave capillary discharges and to a system suitable for this purpose.

For vacuum applications there are many designs of plasma sources whose development has been driven by the demand for production of ever smaller structures with minimal damage to the substrates by the plasma, after the homogeneous processing of ever larger areas and after short processing times. The core of the project is to achieve an optimal plasma composition for processing and to control it in time and place. In the face of ever-increasing demands, there is an urgent need to further develop plasma sources in the future.

Disadvantage of the prior art is that the standing wave decreases when the plasma ignites, and thus also the coupling over the coupling means decreases until the coupling-out energy is no longer sufficient to maintain a stable wave with plasma.

The object of the invention is therefore to improve the control of the micro-plasma sources for these applications.

Disclosure of the invention

According to the invention, there is provided a plasma generating apparatus comprising a plasma source formed as a cavity and a resonator comprising a waveguide and the plasma source, the waveguide being operatively connected to the plasma source; a device having a first coupling means for energy supply and a second coupling means for energy decoupling, each coupling means is energy and signal leading to the waveguide operatively connected; a device having an active element for powering the resonator, which is operatively connected to the first and the second coupling means; wherein the plasma source is at least partially integrated in a portion of the waveguide extending between the first coupling means and the second coupling means.

On one side of the resonator, still belonging to the resonator, there is a first line termination. There, the waveguide is closed to ground, so short-circuited, so that the wave is totally reflected at this point and therefore changes their direction of propagation. Then the wave runs against the plasma and is partially reflected there. Part of the energy goes into the plasma, the other part of the energy goes back to the short circuit with the wave, where again a reflection occurs. Again another part of the wave passes over the plasma towards a second end of the line, where again a reflection takes place. The wave thus runs back and forth several times and is partially absorbed by the plasma, which corresponds to the output into the plasma active power. By going back and forth running creates a resonance / standing wave with voltage increase in the plasma electrodes.

In the embodiment of the invention, the wave also runs into the plasma and is thereby partially reflected, absorbed and additionally transmitted. That is, a part of the wave, the transmitted part, is available for the feedback of the oscillator. What is new is that the plasma is thus actively involved in the feedback in the oscillator and thus has considerably more influence on the oscillator than is the case in the prior art.

The advantage of this device is that the performance of microwave plasma sources with respect to the plasma-dependent tracking of the frequency and the feedback required for the oscillator is improved.

The feedback is not only via direct coupling to the standing wave of the resonator, but according to the invention via the plasma. As the conductivity of the Plasmas increased with its ignition, thus increasing the degree of feedback. This is the gist of the invention and is the advantage of this oscillator type. Furthermore, there are advantages in adjusting the plasma load. The performance, the efficiency, the stability of the oscillation and the reliability are also significantly improved.

Connectedness in the aforementioned sense means preferably be operatively connected, z. By conducting one or more measurands or states. For example, an electric and / or magnetic field may be detected, preferably near the plasma or in or on the resonator or at / through a coupling site. Likewise, an electrical current and / or an electric power could be detected in, at the edge or close to the aforementioned functional elements and the elements for detecting are located there and / or located by directing the physical quantities away from the location of the detection. Likewise, in the area of the plasma source, a dynamic and / or static pressure can be detected. It is also possible to exert optical control of the plasma by means of glass fiber cables and preferably to monitor frequency, phases and performance. It is also possible that the wiring of the elements according to the principle of a crossbar, Umschaltbox, matrix switch, switch, selector, crossover switch or matrix switch is configured, so a controller is used for switching through various signal sources, preferably resonators, to one or several consumers, preferably plasma sources. It is also possible that this switching takes place in the time division multiplex and / or in the local multiplex. It is also possible that the superposition principle is used in order to temporarily superimpose individual resonators in combination with the preferred crossbar principle in order to preferably produce or maintain breakdown voltages or operating points on the part of preferably dedicated plasma sources by spatially and temporally targeted superimposition. In other words, it is possible to achieve the targeted activation of plasma sources, inter alia, by combining the superposition principle, time multiplex and crossbar principle. It is also possible that the plasma source is integrated in the resonator. Also, the resonator may be part of the plasma source. Also, the feed can, without detour via the resonator, be directly operatively connected to the plasma source. The plasma source may comprise the resonator or itself be a part of the resonator.

It is also possible for the plasma source to be completely integrated in a region of the waveguide which extends between the first coupling means and the second coupling means. The extension of the waveguide may take any route through the room, e.g. B. meandering. For example, the plasma source is the supply on the left side and the decoupling on the right side, wherein the plasma source is preferably contacted by waveguides on both sides and the input or output takes place at the waveguide.

It is also possible that the waveguide between the first coupling means and the second coupling means is continuous, and the plasma source is arranged in the course of the waveguide. In this case, continuous does not mean that the waveguide is the same type and / or the same dielectric at each point of the waveguide. Rather, differently constructed path sections are conceivable, wherein continuously means in this context that one and the same wave propagates along a continuous path.

It is also possible that the resonator is a microwave resonator, so that this generates electromagnetic waves in the frequency range typical for microwaves. It is also possible that in the resonator microwaves in the range of 1 to 300 GHz, preferably 1 to 100 GHz, more preferably 1 to 50 GHz and more preferably 1 to 10 GHz are generated.

It is also possible that the resonator comprises a cavity resonator or a descendant of the cavity resonator. It is also possible that the resonator comprises a klystron or a derivative of the klystron. It is also possible that the resonator comprises a cathode ray tube or a derivative of the cathode ray tube. It is also possible that the resonator comprises a Gunn diode or a Gunn element or a derivative of the Gunn element. It is also possible that the resonator is an avalanche diode or a derivative of the avalanche diode, such. For example, an Impatt, Trapatt, Suppressor, Zener or Avalanche photo diode comprises. It is also possible that the resonator is a Dovett diode or a derivative of the Dovett diode, z. B. a Baritt diode includes. It is also possible for the feed means and the resonator to be combined in one component and / or to cooperate so closely that they preferably can not be regarded as separate components and / or must be considered.

It is also possible that the plasma source is formed as a cavity with opening for gas supply and gas discharge. This would have the advantage of being able to do additional mechanical work with the plasma, such as. B. selectively ablate surfaces or workpieces.

It is also possible that the plasma source has a gas supply, which is connected to a first end of the hollow cylindrical tube.

It is also possible for the plasma source to have a gas supply which is not connected to a first end of the hollow-cylindrical tube but feeds the gas between both ends of the tube, preferably through annularly arranged inlet holes, inlet nozzles or gas-directional formers which are defined by appropriate formation of the inner surface become.

It is also possible that this gas supply is fed not only once, but regularly with gas, the regular forwarding of gas accordingly belongs to the preferably regular operating condition and expressly not for one-off technological construction.

It is also possible that the plasma source has a hollow cylindrical tube whose longitudinal axis extends within the microwave resonator perpendicular to the propagation direction of the microwaves.

It is also possible for a rectangular section through the hollow cylindrical tube, not necessarily exactly, but typically, to represent the sectional surface of a polygon, square, triangle, ellipse or rectangle, the section surface reproducing the inner region of the hollow cylindrical tube similar.

It is also possible that a deviation from the right angle takes place in the otherwise preferably perpendicular to the propagation direction of the microwave longitudinal axis of the hollow cylindrical tube.

It is also possible that the active element comprises a transistor. In a preferred embodiment, the transistor operates in positive feedback, so as to use frequency and phase for the time-correct feed. It is also conceivable to use the nonlinearity of the transistor in order to avoid impermissible swinging, so that the nonlinearity acts as a negative feedback despite coupling in positive feedback and thus exerts a certain control function. It is also conceivable to distribute the influences of a positive feedback and negative feedback on separate components or separate groups of components and to let them act together in a combined manner on the resonator, z. B. also via other coupling sites.

It is also possible for the waveguide to comprise a conductor carrying the electrical potential of the shaft, which conductor is through-contacted by means of coupling means and is operatively connected to the energy supply and to the energy decoupling.

It is also possible for the first coupling means to be arranged outside a dedicated location in a region of the waveguide, the dedicated location being at a distance from a first line termination and for this distance having the following formation specification: distance = integer multiple of a half wavelength + one quarter of the wavelength Wavelength. By wavelength is meant that wavelength of the standing wave in the resonator, which is typical for the corresponding dimensioning of the resonator, wherein z. B. the length of the path over all sections of the waveguide and the size of the plasma source influence the resulting wavelength.

The first coupling means for energy supply is thus arranged at that point of a path of the waveguide whose distance from a line termination is different from the sum of a quarter of the wavelength and an integer multiple of half the wavelength; wherein the course path is to be understood as the sum of all path sections, starting at the first line termination with reflection, away via waveguide sections, via the plasma source, via a further waveguide section, up to the second line termination, for reflection where the pathway ends.

1. a) Auskopplung von Energie in Form eines zeitlich und/oder spektral modulierten Signals mit direkter und/oder indirekter Information über den momentanen Schwingungszustand an einem zweiten Kopplungsmittel des Resonators ;
2. b) Zuführung des Signals zu einem aktiven Element;
3. c) Verstärkung des Signals durch das aktive Element in Abhängigkeit vom Schwingungszustand im Resonator;
4. d) Zuführung des verstärkten und zeitlich und/oder spektral modulierten Signals als Speise-Energie in den Resonator an einem ersten Kopplungsmittel;

wobei die Plasmaquelle zwischen dem ersten und dem zweiten Kopplungsmittel angeordnet ist.The invention describes a method for generating a plasma by regulated and / or controlled supply of energy into a resonator comprising a plasma source, having the following method steps:

1. a) decoupling energy in the form of a temporally and / or spectrally modulated signal with direct and / or indirect information about the instantaneous vibration state at a second coupling means of the resonator;
2. b) supplying the signal to an active element;
3. c) amplification of the signal by the active element as a function of the vibration state in the resonator;
4. d) supplying the amplified and temporally and / or spectrally modulated signal as feeding energy into the resonator at a first coupling means;

wherein the plasma source is disposed between the first and second coupling means.

The advantage of this method is that the performance of microwave plasma sources with respect to the plasma-dependent tracking of the frequency and the feedback required for the oscillator is improved. Furthermore, this results in advantages when adjusting the plasma load. The performance, the efficiency, the stability of the oscillation and the reliability are also significantly improved.

It is also possible for the electrical power to be determined as the physical parameter of the plasma source.

Furthermore, it is possible for an electrical current, the temperature, the static and / or dynamic pressure, a magnetic field, an electrical voltage, an electric field, a light intensity, a particle velocity or a force to be determined as the physical parameter of the plasma source. It is also possible that the aforementioned variables change their values as a function of time, ie are dynamic variables. Likewise, it is possible that of those aforementioned variables, which are not scalar quantities, the direction vectors and / or their temporal change are detected. It is also possible that quantities derived from the aforementioned variables are detected, eg. B. from current and voltage, a resistance is derived or from an AC resistance of a capacitance, the frequency is derived.

It is also possible to determine a time-dependent, ie dynamic, complex resistance of a two-pole. A bipolar in this sense can z. Example, the plasma source, the resonator or the feeding means or a series circuit of these elements. This advantageously leads to predeterminability or recognizability based on learned or known points and patterns in the frequency and / or time domain of the complex resistor.

It is also possible, in a LUT, lookup table, to store the connection between controlled variable and manipulated variable which is necessary for the control. This has the advantage of fast access without any loss of computing time.

It is also possible to solve the control tasks by means of calculation paths firmly anchored in FPGA, by a microcontroller or a microprocessor or a combination of some or all of the aforementioned elements (including LUT interpolation).

It is also possible that the method steps a) to d) are repeated within a predefinable time interval. It is also possible that the method steps a) to d) run continuously. It is also possible that the method steps a) to d) do not run continuously but at discrete points in time, for example due to digital processing.

It is also possible that the repetitive time interval is less than 1 s and preferably even less than 0.1 s.

drawings

Figur 1

eine konventionelle Oszillatorvorrichtung zur Erzeugung eines Plasmas für Mikrowellen-Plasmaquellen nach dem Stand der Technik,

Figur 2

eine erfindungsgemäße Oszillatorvorrichtung zur Erzeugung eines Plasmas für Mikrowellen-Plasmaquellen.

The invention will be explained in more detail with reference to the drawings and the description below. Show it:

FIG. 1

a conventional oscillator device for generating a plasma for microwave plasma sources according to the prior art,

FIG. 2

an oscillator device according to the invention for generating a plasma for microwave plasma sources.

FIG. 1 shows a conventional device 100 for generating a plasma 141 according to the prior art. The dashed line 101 indicates the limit of the resonator concept according to the prior art. Here are 121 and 122 line terminations, which lead to the reflection of the electromagnetic wave and thus represent the basis of the vibration in the resonator 101, symbolized as electrical ground. Between the first line termination 121, along the waveguide sections 110, 111, 112, through the plasma 141, up to the second line termination 122, the standing wave builds up whose wave peak, energy maximum, is formed at the location of the plasma source 141, since there largest field strength is needed for ignition and maintenance of the plasma. The coupling site 132 is a contact of the waveguide 110, 111 such that energy is coupled out 152 to be routed to the active element 161. The active element, preferably comprising a transistor connected in preferably positive feedback, thus receives information about frequency and phase in the resonator 101, amplifies the energy and supplies the energy 151 by means of coupling point 131, located at the waveguide 111, 112, the resonator 101 to the To advance the vibration. It is typical of this prior art resonator concept that the coupling points for energy feed 131 and energy decoupling 132 are disposed only between the first line termination 121 and the plasma source 141 and just not between plasma source 141 and second line termination 122th

FIG. 2 shows the inventive device 200 for generating a plasma 241. The dashed line 201 indicates the limit of the resonator concept according to the invention. Here are 221 and 222 line terminations, which lead to the reflection of the electromagnetic wave and thus represent the basis of the vibration in the resonator 201, symbolized as electrical ground. Between the first line termination 221, along the waveguide sections 211, 212, through the plasma 241, along the waveguide 213, up to the second line termination 222, the standing wave whose wave peak, energy maximum, is formed at the location of the plasma source 241, builds up, because there the largest field strength for ignition and maintenance of the plasma is needed.

A section 211, 212, 241, 213 of the waveguide can be recognized by being delimited by a coupling point 231, 232, the plasma source 241 or the line termination 221, 222, ie, the homogeneity of the medium of the waveguide changes along the propagation path of the wave or is interrupted.

The decoupling 252 of energy from the resonator 201 takes place at the coupling point 232 and the supply 251 of energy into the resonator 201 takes place at the coupling point 231, the plasma source 241 being arranged according to the invention between the A-231 and the decoupling point 232.

The active element 261 preferably comprises a transistor in circuitry, preferably for positive feedback, to amplify the applied signal 252. It is also possible to use a further active element, which does not work in positive feedback but in negative feedback in order to improve the stability of the oscillation process in the resonator and thus in the plasma. It is also possible to effectively connect the further active element 261 to a further coupling point for coupling out 232 from the resonator 201, and / or to connect the further active element in turn to a further coupling point to the feed 231. Thus, the possibilities of controlling or even controlling the vibration state in the resonator and plasma can be improved. The waveguide outside the cavity of the plasma source preferably takes place via integrated components with stripline (microstrip) manufactured by monolithic microwave integrated circuit (MMIC) technology. Other types of lines are possible in principle, for. B. coaxial line, ribbon cable or hollow conduit. It is also conceivable to form the plasma source in a smaller volume fraction as a cavity, namely Forming spatial sections of the waveguide by a non-gaseous dielectric, which decouples the energy into the plasma towards the gas region and thus initiates and drives the plasma.

The coupling point for feeding into the resonator is preferably outside the lambda quarter range with respect to the conduction path of the plasma wave in the resonator, since at lambda quarter plus an integer multiple of half the wavelength, there is a vibroend. Thus, the feed signal would have to have an amplitude corresponding to the antinode. This is no longer necessary and thus an advantage when coupled outside of the quarter-wave range.

The coupling point is preferably designed as an electrical line, through-contacted to the waveguide. Also, other coupling forms and a combination of those based on other physical quantities are possible, such as: B. coupling by magnetic field, coupling by electric field, coupling by electrical voltage or by electric current.

The coupling site for the extraction of energy could even detect other physical conditions, such. B. light output, pressure, temperature, magnetic field strength, stray fields and other physical quantities, which are derived directly or indirectly from states in the resonator. Therefore, it is conceivable that a coupling site for decoupling does not directly touch the waveguide of the plasma wave, but is located away from the waveguide of the plasma wave. The plasma wave is the standing wave in the resonator which drives the plasma source. It is also conceivable that a coupling point for decoupling is located in or at the plasma source and the feedback information 252 is obtained directly or indirectly from the plasma state. It is also possible that the aforementioned principle of non-direct contact of the waveguide analogously applies to the coupling point for coupling.

LIST OF REFERENCE NUMBERS

100

Conventional device for generating a plasma

101

Resonator according to the prior art

110

waveguides

111

waveguides

112

waveguides

121

Line conclusion for reflection

122

Line conclusion for reflection

131

Coupling means for coupling

132

Coupling means for extraction

141

plasma source

151

Energy supply

152

Energy extraction

161

Active element

200

Inventive device for generating a plasma

201

Resonator with inventive output

211

waveguides

212

waveguides

213

waveguides

221

Line conclusion for reflection

222

Line conclusion for reflection

231

Coupling means for coupling

232

Coupling means for extraction

241

plasma source

251

Energy supply

252

Energy extraction

261

Active element

Claims (10)

A device (200) for generating a plasma, comprising: - A trained as a cavity plasma source (241); - a resonator (201) comprising a waveguide (211, 212, 213) and the plasma source (241), the waveguide (211, 212, 213) being operatively connected to the plasma source (241); - A first coupling means (231) for energy supply (251) and a second coupling means (232) for energy extraction (252), each coupling means (231, 232) energy-conducting and / or signal-carrying with the waveguide (211, 212, 213) is operatively connected; - an active element (261) for powering the resonator (201), which is operatively connected to the first coupling means (231) and to the second coupling means (232); characterized in that
the plasma source (241) is at least partially integrated in a region of the waveguide (211, 212, 213) extending between the first coupling means (231) and the second coupling means (232). Device (200) according to claim 1,
characterized in that
the plasma source (241) is fully integrated in a portion of the waveguide (211, 212, 213) extending between the first coupling means (231) and the second coupling means (232). Device (200) according to one of the preceding claims,
characterized in that
the waveguide (211, 212, 213) runs continuously between the first coupling means (231) and the second coupling means (232), and the plasma source (241) is arranged in this continuously extending region of the waveguide (211, 212, 213). Device (200) according to one of the preceding claims,
characterized in that
the resonator (201) is a microwave resonator. Device (200) according to one of the preceding claims,
characterized in that
the plasma source (241) is formed as a cavity with opening for gas supply and gas discharge. Device (200) according to claim 4,
characterized in that
the plasma source (241) has a waveguide whose longitudinal axis extends within the microwave resonator (201) perpendicular to the propagation direction of the microwaves. Device (200) according to one of the preceding claims,
characterized in that
the active element (261) comprises a transistor. Device (200) according to one of the preceding claims,
characterized in that
the waveguide (211, 212, 213) comprises an electrical conductor, wherein the electrical conductor directly contacts the first coupling means (231) and / or directly contacts the second coupling means (232). Device (200) according to one of the preceding claims,
characterized in that
the waveguide (211, 212, 213) has a first line termination (221) for reflecting a wave and a second line termination (222) for reflecting a wave, wherein the first coupling means (231) is arranged between the line terminations (221, 222), and the distance A of the first coupling means (231) from the first line termination (221) of the condition $$\mathrm{A}\mathrm{\ne }\mathrm{n}\mathrm{*}\mathrm{\lambda }\mathrm{/}\mathrm{2}\mathrm{+}\mathrm{\lambda }\mathrm{/}\mathrm{4}$$

is sufficient, where n is an integer and λ is the resonant wavelength of the resonator (201). A method of generating a plasma by injecting energy into a resonator (201) comprising a plasma source (241), the plasma source (241) being arranged between a first (231) and a second (232) coupling means, comprising the following method steps: a) coupling (252) of energy in the form of a modulated signal with information about the vibration state at the second coupling means (232) of the resonator (201); b) supplying the signal (252) to an active element (261); c) amplifying the signal (252) by the active element (261) as a function of the vibration state in the resonator (201); d) supplying (251) the amplified signal into the resonator as feed energy (201) at the first coupling means (231).

Images